diff --git a/src/Language/AST/FragmentDefinition.php b/src/Language/AST/FragmentDefinition.php
index 8715584..095aa68 100644
--- a/src/Language/AST/FragmentDefinition.php
+++ b/src/Language/AST/FragmentDefinition.php
@@ -2,7 +2,7 @@
 namespace GraphQL\Language\AST;
 
 
-class FragmentDefinition extends Node implements Definition
+class FragmentDefinition extends Node implements Definition, HasSelectionSet
 {
     public $kind = Node::FRAGMENT_DEFINITION;
 
diff --git a/src/Language/AST/HasSelectionSet.php b/src/Language/AST/HasSelectionSet.php
new file mode 100644
index 0000000..54872dd
--- /dev/null
+++ b/src/Language/AST/HasSelectionSet.php
@@ -0,0 +1,10 @@
+<?php
+namespace GraphQL\Language\AST;
+
+interface HasSelectionSet
+{
+    /**
+     * export type Definition = OperationDefinition
+     *                        | FragmentDefinition
+     */
+}
diff --git a/src/Language/AST/OperationDefinition.php b/src/Language/AST/OperationDefinition.php
index 681f07d..7e05fec 100644
--- a/src/Language/AST/OperationDefinition.php
+++ b/src/Language/AST/OperationDefinition.php
@@ -1,7 +1,7 @@
 <?php
 namespace GraphQL\Language\AST;
 
-class OperationDefinition extends Node implements Definition
+class OperationDefinition extends Node implements Definition, HasSelectionSet
 {
     /**
      * @var string
diff --git a/src/Language/Visitor.php b/src/Language/Visitor.php
index 777c587..8ab3fac 100644
--- a/src/Language/Visitor.php
+++ b/src/Language/Visitor.php
@@ -2,12 +2,10 @@
 namespace GraphQL\Language;
 
 use GraphQL\Language\AST\Node;
+use GraphQL\Utils\TypeInfo;
 
 class Visitor
 {
-    const BREAK_VISIT = '@@BREAK@@';
-    const CONTINUE_VISIT = '@@CONTINUE@@';
-
     /**
      * Break visitor
      *
@@ -244,7 +242,7 @@ class Visitor
                     throw new \Exception('Invalid AST Node: ' . json_encode($node));
                 }
 
-                $visitFn = self::getVisitFn($visitor, $isLeaving, $node->kind);
+                $visitFn = self::getVisitFn($visitor, $node->kind, $isLeaving);
 
                 if ($visitFn) {
                     $result = call_user_func($visitFn, $node, $key, $parent, $path, $ancestors);
@@ -308,13 +306,100 @@ class Visitor
         return $newRoot;
     }
 
+    /**
+     * @param $visitors
+     * @return array
+     */
+    static function visitInParallel($visitors)
+    {
+        // TODO: implement real parallel visiting once PHP supports it
+        $visitorsCount = count($visitors);
+        $skipping = new \SplFixedArray($visitorsCount);
+
+        return [
+            'enter' => function ($node) use ($visitors, $skipping, $visitorsCount) {
+                for ($i = 0; $i < $visitorsCount; $i++) {
+                    if (empty($skipping[$i])) {
+                        $fn = self::getVisitFn($visitors[$i], $node->kind, /* isLeaving */ false);
+
+                        if ($fn) {
+                            $result = call_user_func_array($fn, func_get_args());
+
+                            if ($result instanceof VisitorOperation) {
+                                if ($result->doContinue) {
+                                    $skipping[$i] = $node;
+                                } else if ($result->doBreak) {
+                                    $skipping[$i] = $result;
+                                }
+                            } else if ($result !== null) {
+                                return $result;
+                            }
+                        }
+                    }
+                }
+            },
+            'leave' => function ($node) use ($visitors, $skipping, $visitorsCount) {
+                for ($i = 0; $i < $visitorsCount; $i++) {
+                    if (empty($skipping[$i])) {
+                        $fn = self::getVisitFn($visitors[$i], $node->kind, /* isLeaving */ true);
+
+                        if ($fn) {
+                            $result = call_user_func_array($fn, func_get_args());
+                            if ($result instanceof VisitorOperation) {
+                                if ($result->doBreak) {
+                                    $skipping[$i] = $result;
+                                }
+                            } else if ($result !== null) {
+                                return $result;
+                            }
+                        }
+                    } else if ($skipping[$i] === $node) {
+                        $skipping[$i] = null;
+                    }
+                }
+            }
+        ];
+    }
+
+    /**
+     * Creates a new visitor instance which maintains a provided TypeInfo instance
+     * along with visiting visitor.
+     */
+    static function visitWithTypeInfo(TypeInfo $typeInfo, $visitor)
+    {
+        return [
+            'enter' => function ($node) use ($typeInfo, $visitor) {
+                $typeInfo->enter($node);
+                $fn = self::getVisitFn($visitor, $node->kind, false);
+
+                if ($fn) {
+                    $result = call_user_func_array($fn, func_get_args());
+                    if ($result) {
+                        $typeInfo->leave($node);
+                        if ($result instanceof Node) {
+                            $typeInfo->enter($result);
+                        }
+                    }
+                    return $result;
+                }
+                return null;
+            },
+            'leave' => function ($node) use ($typeInfo, $visitor) {
+                $fn = self::getVisitFn($visitor, $node->kind, true);
+                $result = $fn ? call_user_func_array($fn, func_get_args()) : null;
+                $typeInfo->leave($node);
+                return $result;
+            }
+        ];
+    }
+
     /**
      * @param $visitor
-     * @param $isLeaving
      * @param $kind
+     * @param $isLeaving
      * @return null
      */
-    public static function getVisitFn($visitor, $isLeaving, $kind)
+    public static function getVisitFn($visitor, $kind, $isLeaving)
     {
         if (!$visitor) {
             return null;
diff --git a/src/Schema.php b/src/Schema.php
index 134d9f8..6940d45 100644
--- a/src/Schema.php
+++ b/src/Schema.php
@@ -1,6 +1,7 @@
 <?php
 namespace GraphQL;
 
+use GraphQL\Type\Definition\AbstractType;
 use GraphQL\Type\Definition\Directive;
 use GraphQL\Type\Definition\FieldArgument;
 use GraphQL\Type\Definition\FieldDefinition;
@@ -16,37 +17,128 @@ use GraphQL\Type\Introspection;
 
 class Schema
 {
-    protected $querySchema;
+    /**
+     * @var ObjectType
+     */
+    protected $_queryType;
 
-    protected $mutationSchema;
+    /**
+     * @var ObjectType
+     */
+    protected $_mutationType;
 
-    protected $subscriptionSchema;
-
-    protected $_typeMap;
+    /**
+     * @var ObjectType
+     */
+    protected $_subscriptionType;
 
+    /**
+     * @var Directive[]
+     */
     protected $_directives;
 
-    public function __construct(Type $querySchema = null, Type $mutationSchema = null, Type $subscriptionSchema = null)
-    {
-        Utils::invariant($querySchema || $mutationSchema, "Either query or mutation type must be set");
-        $this->querySchema = $querySchema;
-        $this->mutationSchema = $mutationSchema;
-        $this->subscriptionSchema = $subscriptionSchema;
+    /**
+     * @var array<string, Type>
+     */
+    protected $_typeMap;
 
-        InterfaceType::loadImplementationToInterfaces();
+    /**
+     * @var array<string, ObjectType[]>
+     */
+    protected $_implementations;
+
+    /**
+     * @var array<string, array<string, boolean>>
+     */
+    protected $_possibleTypeMap;
+
+    /**
+     * Schema constructor.
+     * @param array $config
+     */
+    public function __construct($config = null)
+    {
+        if (func_num_args() > 1 || $config instanceof Type) {
+            trigger_error(
+                'GraphQL\Schema constructor expects config object now instead of types passed as arguments. '.
+                'See https://github.com/webonyx/graphql-php/issues/36',
+                E_USER_DEPRECATED
+            );
+            list($queryType, $mutationType, $subscriptionType) = func_get_args();
+
+            $config = [
+                'query' => $queryType,
+                'mutation' => $mutationType,
+                'subscription' => $subscriptionType
+            ];
+        }
+
+        $this->_init($config);
+    }
+
+    protected function _init(array $config)
+    {
+        Utils::invariant(isset($config['query']) || isset($config['mutation']), "Either query or mutation type must be set");
+
+        $config += [
+            'query' => null,
+            'mutation' => null,
+            'subscription' => null,
+            'directives' => [],
+            'validate' => true
+        ];
+
+        $this->_queryType = $config['query'];
+        $this->_mutationType = $config['mutation'];
+        $this->_subscriptionType = $config['subscription'];
+
+        $this->_directives = array_merge($config['directives'], [
+            Directive::includeDirective(),
+            Directive::skipDirective()
+        ]);
 
         // Build type map now to detect any errors within this schema.
+        $initialTypes = [
+            $config['query'],
+            $config['mutation'],
+            $config['subscription'],
+            Introspection::_schema()
+        ];
+        if (!empty($config['types'])) {
+            $initialTypes = array_merge($initialTypes, $config['types']);
+        }
+
         $map = [];
-        foreach ([$this->getQueryType(), $this->getMutationType(), Introspection::_schema()] as $type) {
+        foreach ($initialTypes as $type) {
             $this->_extractTypes($type, $map);
         }
         $this->_typeMap = $map + Type::getInternalTypes();
 
+        // Keep track of all implementations by interface name.
+        $this->_implementations = [];
+        foreach ($this->_typeMap as $typeName => $type) {
+            if ($type instanceof ObjectType) {
+                foreach ($type->getInterfaces() as $iface) {
+                    $this->_implementations[$iface->name][] = $type;
+                }
+            }
+        }
+
+        if ($config['validate']) {
+            $this->validate();
+        }
+    }
+
+    /**
+     * Additionaly validate schema for integrity
+     */
+    public function validate()
+    {
         // Enforce correct interface implementations
         foreach ($this->_typeMap as $typeName => $type) {
             if ($type instanceof ObjectType) {
                 foreach ($type->getInterfaces() as $iface) {
-                    $this->assertObjectImplementsInterface($type, $iface);
+                    $this->_assertObjectImplementsInterface($type, $iface);
                 }
             }
         }
@@ -57,7 +149,7 @@ class Schema
      * @param InterfaceType $iface
      * @throws \Exception
      */
-    private function assertObjectImplementsInterface(ObjectType $object, InterfaceType $iface)
+    protected function _assertObjectImplementsInterface(ObjectType $object, InterfaceType $iface)
     {
         $objectFieldMap = $object->getFields();
         $ifaceFieldMap = $iface->getFields();
@@ -73,7 +165,7 @@ class Schema
             $objectField = $objectFieldMap[$fieldName];
 
             Utils::invariant(
-                $this->isEqualType($ifaceField->getType(), $objectField->getType()),
+                $this->_isEqualType($ifaceField->getType(), $objectField->getType()),
                 "$iface.$fieldName expects type \"{$ifaceField->getType()}\" but " .
                 "$object.$fieldName provides type \"{$objectField->getType()}"
             );
@@ -93,7 +185,7 @@ class Schema
                 // Assert interface field arg type matches object field arg type.
                 // (invariant)
                 Utils::invariant(
-                    $this->isEqualType($ifaceArg->getType(), $objectArg->getType()),
+                    $this->_isEqualType($ifaceArg->getType(), $objectArg->getType()),
                     "$iface.$fieldName($argName:) expects type \"{$ifaceArg->getType()}\" " .
                     "but $object.$fieldName($argName:) provides " .
                     "type \"{$objectArg->getType()}\""
@@ -118,35 +210,105 @@ class Schema
      * @param $typeB
      * @return bool
      */
-    private function isEqualType($typeA, $typeB)
+    protected function _isEqualType($typeA, $typeB)
     {
         if ($typeA instanceof NonNull && $typeB instanceof NonNull) {
-            return $this->isEqualType($typeA->getWrappedType(), $typeB->getWrappedType());
+            return $this->_isEqualType($typeA->getWrappedType(), $typeB->getWrappedType());
         }
         if ($typeA instanceof ListOfType && $typeB instanceof ListOfType) {
-            return $this->isEqualType($typeA->getWrappedType(), $typeB->getWrappedType());
+            return $this->_isEqualType($typeA->getWrappedType(), $typeB->getWrappedType());
         }
         return $typeA === $typeB;
     }
 
+    /**
+     * @return ObjectType
+     */
     public function getQueryType()
     {
-        return $this->querySchema;
+        return $this->_queryType;
     }
 
+    /**
+     * @return ObjectType
+     */
     public function getMutationType()
     {
-        return $this->mutationSchema;
+        return $this->_mutationType;
     }
 
+    /**
+     * @return ObjectType
+     */
     public function getSubscriptionType()
     {
-        return $this->subscriptionSchema;
+        return $this->_subscriptionType;
+    }
+
+    /**
+     * @return array
+     */
+    public function getTypeMap()
+    {
+        return $this->_typeMap;
+    }
+
+    /**
+     * @param string $name
+     * @return Type
+     */
+    public function getType($name)
+    {
+        $map = $this->getTypeMap();
+        return isset($map[$name]) ? $map[$name] : null;
+    }
+
+    /**
+     * @param AbstractType $abstractType
+     * @return ObjectType[]
+     */
+    public function getPossibleTypes(AbstractType $abstractType)
+    {
+        if ($abstractType instanceof UnionType) {
+            return $abstractType->getTypes();
+        }
+        Utils::invariant($abstractType instanceof InterfaceType);
+        return $this->_implementations[$abstractType->name];
+    }
+
+    /**
+     * @param AbstractType $abstractType
+     * @param ObjectType $possibleType
+     * @return bool
+     */
+    public function isPossibleType(AbstractType $abstractType, ObjectType $possibleType)
+    {
+        if (null === $this->_possibleTypeMap) {
+            $this->_possibleTypeMap = [];
+        }
+
+        if (!isset($this->_possibleTypeMap[$abstractType->name])) {
+            $tmp = [];
+            foreach ($this->getPossibleTypes($abstractType) as $type) {
+                $tmp[$type->name] = true;
+            }
+            $this->_possibleTypeMap[$abstractType->name] = $tmp;
+        }
+
+        return !empty($this->_possibleTypeMap[$abstractType->name][$possibleType->name]);
+    }
+
+    /**
+     * @return Directive[]
+     */
+    public function getDirectives()
+    {
+        return $this->_directives;
     }
 
     /**
      * @param $name
-     * @return null
+     * @return Directive
      */
     public function getDirective($name)
     {
@@ -158,26 +320,7 @@ class Schema
         return null;
     }
 
-    /**
-     * @return array<Directive>
-     */
-    public function getDirectives()
-    {
-        if (!$this->_directives) {
-            $this->_directives = [
-                Directive::includeDirective(),
-                Directive::skipDirective()
-            ];
-        }
-        return $this->_directives;
-    }
-
-    public function getTypeMap()
-    {
-        return $this->_typeMap;
-    }
-
-    private function _extractTypes($type, &$map)
+    protected function _extractTypes($type, &$map)
     {
         if (!$type) {
             return $map;
@@ -198,8 +341,8 @@ class Schema
 
         $nestedTypes = [];
 
-        if ($type instanceof InterfaceType || $type instanceof UnionType) {
-            $nestedTypes = $type->getPossibleTypes();
+        if ($type instanceof UnionType) {
+            $nestedTypes = $type->getTypes();
         }
         if ($type instanceof ObjectType) {
             $nestedTypes = array_merge($nestedTypes, $type->getInterfaces());
@@ -218,10 +361,4 @@ class Schema
         }
         return $map;
     }
-
-    public function getType($name)
-    {
-        $map = $this->getTypeMap();
-        return isset($map[$name]) ? $map[$name] : null;
-    }
 }
diff --git a/src/Type/Definition/AbstractType.php b/src/Type/Definition/AbstractType.php
index 453af24..7b99cc1 100644
--- a/src/Type/Definition/AbstractType.php
+++ b/src/Type/Definition/AbstractType.php
@@ -12,16 +12,16 @@ GraphQLUnionType;
     /**
      * @return array<ObjectType>
      */
-    public function getPossibleTypes();
+    // public function getPossibleTypes();
 
     /**
      * @return ObjectType
      */
-    public function getObjectType($value, ResolveInfo $info);
+    // public function getObjectType($value, ResolveInfo $info);
 
     /**
      * @param Type $type
      * @return bool
      */
-    public function isPossibleType(Type $type);
+    // public function isPossibleType(Type $type);
 }
diff --git a/src/Type/Definition/Directive.php b/src/Type/Definition/Directive.php
index abb9b41..ae09422 100644
--- a/src/Type/Definition/Directive.php
+++ b/src/Type/Definition/Directive.php
@@ -5,6 +5,16 @@ class Directive
 {
     public static $internalDirectives;
 
+    public static $directiveLocations = [
+        'QUERY' => 'QUERY',
+        'MUTATION' => 'MUTATION',
+        'SUBSCRIPTION' => 'SUBSCRIPTION',
+        'FIELD' => 'FIELD',
+        'FRAGMENT_DEFINITION' => 'FRAGMENT_DEFINITION',
+        'FRAGMENT_SPREAD' => 'FRAGMENT_SPREAD',
+        'INLINE_FRAGMENT' => 'INLINE_FRAGMENT',
+    ];
+
     /**
      * @return Directive
      */
@@ -30,6 +40,11 @@ class Directive
                 'include' => new self([
                     'name' => 'include',
                     'description' => 'Directs the executor to include this field or fragment only when the `if` argument is true.',
+                    'locations' => [
+                        self::$directiveLocations['FIELD'],
+                        self::$directiveLocations['FRAGMENT_SPREAD'],
+                        self::$directiveLocations['INLINE_FRAGMENT'],
+                    ],
                     'args' => [
                         new FieldArgument([
                             'name' => 'if',
@@ -37,23 +52,22 @@ class Directive
                             'description' => 'Included when true.'
                         ])
                     ],
-                    'onOperation' => false,
-                    'onFragment' => true,
-                    'onField' => true
                 ]),
                 'skip' => new self([
                     'name' => 'skip',
                     'description' => 'Directs the executor to skip this field or fragment when the `if` argument is true.',
+                    'locations' => [
+                        self::$directiveLocations['FIELD'],
+                        self::$directiveLocations['FRAGMENT_SPREAD'],
+                        self::$directiveLocations['INLINE_FRAGMENT']
+                    ],
                     'args' => [
                         new FieldArgument([
                             'name' => 'if',
                             'type' => Type::nonNull(Type::boolean()),
                             'description' => 'Skipped when true'
                         ])
-                    ],
-                    'onOperation' => false,
-                    'onFragment' => true,
-                    'onField' => true
+                    ]
                 ])
             ];
         }
@@ -70,26 +84,18 @@ class Directive
      */
     public $description;
 
+    /**
+     * Values from self::$locationMap
+     *
+     * @var array
+     */
+    public $locations;
+
     /**
      * @var FieldArgument[]
      */
     public $args;
 
-    /**
-     * @var boolean
-     */
-    public $onOperation;
-
-    /**
-     * @var boolean
-     */
-    public $onFragment;
-
-    /**
-     * @var boolean
-     */
-    public $onField;
-
     public function __construct(array $config)
     {
         foreach ($config as $key => $value) {
diff --git a/src/Type/Definition/UnionType.php b/src/Type/Definition/UnionType.php
index cd6cfcf..9fcdac9 100644
--- a/src/Type/Definition/UnionType.php
+++ b/src/Type/Definition/UnionType.php
@@ -6,7 +6,7 @@ use GraphQL\Utils;
 class UnionType extends Type implements AbstractType, OutputType, CompositeType
 {
     /**
-     * @var Array<GraphQLObjectType>
+     * @var ObjectType[]
      */
     private $_types;
 
@@ -48,10 +48,16 @@ class UnionType extends Type implements AbstractType, OutputType, CompositeType
         $this->_config = $config;
     }
 
-    /**
-     * @return array<ObjectType>
-     */
     public function getPossibleTypes()
+    {
+        trigger_error(__METHOD__ . ' is deprecated in favor of ' . __CLASS__ . '::getTypes()', E_USER_DEPRECATED);
+        return $this->getTypes();
+    }
+
+    /**
+     * @return ObjectType[]
+     */
+    public function getTypes()
     {
         if ($this->_types instanceof \Closure) {
             $this->_types = call_user_func($this->_types);
@@ -71,7 +77,7 @@ class UnionType extends Type implements AbstractType, OutputType, CompositeType
 
         if (null === $this->_possibleTypeNames) {
             $this->_possibleTypeNames = [];
-            foreach ($this->getPossibleTypes() as $possibleType) {
+            foreach ($this->getTypes() as $possibleType) {
                 $this->_possibleTypeNames[$possibleType->name] = true;
             }
         }
diff --git a/src/Utils/TypeInfo.php b/src/Utils/TypeInfo.php
index 46ed40c..145b631 100644
--- a/src/Utils/TypeInfo.php
+++ b/src/Utils/TypeInfo.php
@@ -41,7 +41,7 @@ class TypeInfo
             return $innerType ? new NonNull($innerType) : null;
         }
 
-        Utils::invariant($inputTypeAst->kind === Node::NAMED_TYPE, 'Must be a named type');
+        Utils::invariant($inputTypeAst && $inputTypeAst->kind === Node::NAMED_TYPE, 'Must be a named type');
         return $schema->getType($inputTypeAst->name->value);
     }
 
@@ -197,11 +197,7 @@ class TypeInfo
                     // isCompositeType is a type refining predicate, so this is safe.
                     $compositeType = $namedType;
                 }
-                array_push($this->_parentTypeStack, $compositeType);
-                break;
-
-            case Node::DIRECTIVE:
-                $this->_directive = $schema->getDirective($node->name->value);
+                $this->_parentTypeStack[] = $compositeType; // push
                 break;
 
             case Node::FIELD:
@@ -210,8 +206,12 @@ class TypeInfo
                 if ($parentType) {
                     $fieldDef = self::_getFieldDef($schema, $parentType, $node);
                 }
-                array_push($this->_fieldDefStack, $fieldDef);
-                array_push($this->_typeStack, $fieldDef ? $fieldDef->getType() : null);
+                $this->_fieldDefStack[] = $fieldDef; // push
+                $this->_typeStack[] = $fieldDef ? $fieldDef->getType() : null; // push
+                break;
+
+            case Node::DIRECTIVE:
+                $this->_directive = $schema->getDirective($node->name->value);
                 break;
 
             case Node::OPERATION_DEFINITION:
@@ -220,18 +220,22 @@ class TypeInfo
                     $type = $schema->getQueryType();
                 } else if ($node->operation === 'mutation') {
                     $type = $schema->getMutationType();
+                } else if ($node->operation === 'subscription') {
+                    $type = $schema->getSubscriptionType();
                 }
-                array_push($this->_typeStack, $type);
+                $this->_typeStack[] = $type; // push
                 break;
 
             case Node::INLINE_FRAGMENT:
             case Node::FRAGMENT_DEFINITION:
-                $type = self::typeFromAST($schema, $node->typeCondition);
-                array_push($this->_typeStack, $type);
+                $typeConditionAST = $node->typeCondition;
+                $outputType = $typeConditionAST ? self::typeFromAST($schema, $typeConditionAST) : $this->getType();
+                $this->_typeStack[] = $outputType; // push
                 break;
 
             case Node::VARIABLE_DEFINITION:
-                array_push($this->_inputTypeStack, self::typeFromAST($schema, $node->type));
+                $inputType = self::typeFromAST($schema, $node->type);
+                $this->_inputTypeStack[] = $inputType; // push
                 break;
 
             case Node::ARGUMENT:
@@ -244,15 +248,12 @@ class TypeInfo
                     }
                 }
                 $this->_argument = $argDef;
-                array_push($this->_inputTypeStack, $argType);
+                $this->_inputTypeStack[] = $argType; // push
                 break;
 
             case Node::LST:
                 $listType = Type::getNullableType($this->getInputType());
-                array_push(
-                    $this->_inputTypeStack,
-                    $listType instanceof ListOfType ? $listType->getWrappedType() : null
-                );
+                $this->_inputTypeStack[] = ($listType instanceof ListOfType ? $listType->getWrappedType() : null); // push
                 break;
 
             case Node::OBJECT_FIELD:
@@ -263,7 +264,7 @@ class TypeInfo
                     $inputField = isset($tmp[$node->name->value]) ? $tmp[$node->name->value] : null;
                     $fieldType = $inputField ? $inputField->getType() : null;
                 }
-                array_push($this->_inputTypeStack, $fieldType);
+                $this->_inputTypeStack[] = $fieldType;
             break;
         }
     }
diff --git a/src/Validator/DocumentValidator.php b/src/Validator/DocumentValidator.php
index 19c7c50..2e1c828 100644
--- a/src/Validator/DocumentValidator.php
+++ b/src/Validator/DocumentValidator.php
@@ -8,11 +8,13 @@ use GraphQL\Language\AST\FragmentSpread;
 use GraphQL\Language\AST\Node;
 use GraphQL\Language\AST\Value;
 use GraphQL\Language\AST\Variable;
+use GraphQL\Language\Printer;
 use GraphQL\Language\Visitor;
 use GraphQL\Language\VisitorOperation;
 use GraphQL\Schema;
 use GraphQL\Type\Definition\EnumType;
 use GraphQL\Type\Definition\InputObjectType;
+use GraphQL\Type\Definition\InputType;
 use GraphQL\Type\Definition\ListOfType;
 use GraphQL\Type\Definition\NonNull;
 use GraphQL\Type\Definition\ScalarType;
@@ -27,6 +29,7 @@ use GraphQL\Validator\Rules\KnownArgumentNames;
 use GraphQL\Validator\Rules\KnownDirectives;
 use GraphQL\Validator\Rules\KnownFragmentNames;
 use GraphQL\Validator\Rules\KnownTypeNames;
+use GraphQL\Validator\Rules\LoneAnonymousOperation;
 use GraphQL\Validator\Rules\NoFragmentCycles;
 use GraphQL\Validator\Rules\NoUndefinedVariables;
 use GraphQL\Validator\Rules\NoUnusedFragments;
@@ -62,28 +65,31 @@ class DocumentValidator
     {
         if (null === self::$defaultRules) {
             self::$defaultRules = [
-                // new UniqueOperationNames,
-                // new LoneAnonymousOperation,
+                // 'UniqueOperationNames' => new UniqueOperationNames(),
+                'LoneAnonymousOperation' => new LoneAnonymousOperation(),
                 'KnownTypeNames' => new KnownTypeNames(),
                 'FragmentsOnCompositeTypes' => new FragmentsOnCompositeTypes(),
                 'VariablesAreInputTypes' => new VariablesAreInputTypes(),
                 'ScalarLeafs' => new ScalarLeafs(),
                 'FieldsOnCorrectType' => new FieldsOnCorrectType(),
-                // new UniqueFragmentNames,
+                // 'UniqueFragmentNames' => new UniqueFragmentNames(),
                 'KnownFragmentNames' => new KnownFragmentNames(),
                 'NoUnusedFragments' => new NoUnusedFragments(),
                 'PossibleFragmentSpreads' => new PossibleFragmentSpreads(),
                 'NoFragmentCycles' => new NoFragmentCycles(),
+                // 'UniqueVariableNames' => new UniqueVariableNames(),
                 'NoUndefinedVariables' => new NoUndefinedVariables(),
                 'NoUnusedVariables' => new NoUnusedVariables(),
                 'KnownDirectives' => new KnownDirectives(),
                 'KnownArgumentNames' => new KnownArgumentNames(),
-                // new UniqueArgumentNames,
+                // 'UniqueArgumentNames' => new UniqueArgumentNames(),
                 'ArgumentsOfCorrectType' => new ArgumentsOfCorrectType(),
                 'ProvidedNonNullArguments' => new ProvidedNonNullArguments(),
                 'DefaultValuesOfCorrectType' => new DefaultValuesOfCorrectType(),
                 'VariablesInAllowedPosition' => new VariablesInAllowedPosition(),
                 'OverlappingFieldsCanBeMerged' => new OverlappingFieldsCanBeMerged(),
+                // 'UniqueInputFieldNames' => new UniqueInputFieldNames(),
+
                 // Query Security
                 'QueryDepth' => new QueryDepth(QueryDepth::DISABLED), // default disabled
                 'QueryComplexity' => new QueryComplexity(QueryComplexity::DISABLED), // default disabled
@@ -107,7 +113,8 @@ class DocumentValidator
 
     public static function validate(Schema $schema, Document $ast, array $rules = null)
     {
-        $errors = static::visitUsingRules($schema, $ast, $rules ?: static::allRules());
+        $typeInfo = new TypeInfo($schema);
+        $errors = static::visitUsingRules($schema, $typeInfo, $ast, $rules ?: static::allRules());
         return $errors;
     }
 
@@ -128,76 +135,109 @@ class DocumentValidator
         return $arr;
     }
 
-    public static function isValidLiteralValue($valueAST, Type $type)
+    /**
+     * Utility for validators which determines if a value literal AST is valid given
+     * an input type.
+     *
+     * Note that this only validates literal values, variables are assumed to
+     * provide values of the correct type.
+     *
+     * @return array
+     */
+    public static function isValidLiteralValue(Type $type, $valueAST)
     {
-        // A value can only be not provided if the type is nullable.
-        if (!$valueAST) {
-            return !($type instanceof NonNull);
+        // A value must be provided if the type is non-null.
+        if ($type instanceof NonNull) {
+            $wrappedType = $type->getWrappedType();
+            if (!$valueAST) {
+                if ($wrappedType->name) {
+                    return [ "Expected \"{$wrappedType->name}!\", found null." ];
+                }
+                return ['Expected non-null value, found null.'];
+            }
+            return static::isValidLiteralValue($wrappedType, $valueAST);
         }
 
-        // Unwrap non-null.
-        if ($type instanceof NonNull) {
-            return static::isValidLiteralValue($valueAST, $type->getWrappedType());
+        if (!$valueAST) {
+            return [];
         }
 
         // This function only tests literals, and assumes variables will provide
         // values of the correct type.
         if ($valueAST instanceof Variable) {
-            return true;
-        }
-
-        if (!$valueAST instanceof Value) {
-            return false;
+            return [];
         }
 
         // Lists accept a non-list value as a list of one.
         if ($type instanceof ListOfType) {
             $itemType = $type->getWrappedType();
             if ($valueAST instanceof ListValue) {
-                foreach($valueAST->values as $itemAST) {
-                    if (!static::isValidLiteralValue($itemAST, $itemType)) {
-                        return false;
+                $errors = [];
+                foreach($valueAST->values as $index => $itemAST) {
+                    $tmp = static::isValidLiteralValue($itemType, $itemAST);
+
+                    if ($tmp) {
+                        $errors = array_merge($errors, Utils::map($tmp, function($error) use ($index) {
+                            return "In element #$index: $error";
+                        }));
                     }
                 }
-                return true;
+                return $errors;
             } else {
-                return static::isValidLiteralValue($valueAST, $itemType);
+                return static::isValidLiteralValue($itemType, $valueAST);
             }
         }
 
-        // Scalar/Enum input checks to ensure the type can serialize the value to
-        // a non-null value.
-        if ($type instanceof ScalarType || $type instanceof EnumType) {
-            return $type->parseLiteral($valueAST) !== null;
-        }
-
-        // Input objects check each defined field, ensuring it is of the correct
-        // type and provided if non-nullable.
+        // Input objects check each defined field and look for undefined fields.
         if ($type instanceof InputObjectType) {
-            $fields = $type->getFields();
             if ($valueAST->kind !== Node::OBJECT) {
-                return false;
+                return [ "Expected \"{$type->name}\", found not an object." ];
             }
-            $fieldASTs = $valueAST->fields;
-            $fieldASTMap = Utils::keyMap($fieldASTs, function($field) {return $field->name->value;});
 
-            foreach ($fields as $fieldKey => $field) {
-                $fieldName = $field->name ?: $fieldKey;
-                if (!isset($fieldASTMap[$fieldName]) && $field->getType() instanceof NonNull) {
-                    // Required fields missing
-                    return false;
+            $fields = $type->getFields();
+            $errors = [];
+
+            // Ensure every provided field is defined.
+            $fieldASTs = $valueAST->fields;
+
+            foreach ($fieldASTs as $providedFieldAST) {
+                if (empty($fields[$providedFieldAST->name->value])) {
+                    $errors[] = "In field \"{$providedFieldAST->name->value}\": Unknown field.";
                 }
             }
-            foreach ($fieldASTs as $fieldAST) {
-                if (empty($fields[$fieldAST->name->value]) || !static::isValidLiteralValue($fieldAST->value, $fields[$fieldAST->name->value]->getType())) {
-                    return false;
+
+            // Ensure every defined field is valid.
+            $fieldASTMap = Utils::keyMap($fieldASTs, function($fieldAST) {return $fieldAST->name->value;});
+            foreach ($fields as $fieldName => $field) {
+                $result = static::isValidLiteralValue(
+                    $field->getType(),
+                    isset($fieldASTMap[$fieldName]) ? $fieldASTMap[$fieldName]->value : null
+                );
+                if ($result) {
+                    $errors = array_merge($errors, Utils::map($result, function($error) use ($fieldName) {
+                        return "In field \"$fieldName\": $error";
+                    }));
                 }
             }
-            return true;
+
+            return $errors;
         }
 
-        // Any other kind of type is not an input type, and a literal cannot be used.
-        return false;
+        Utils::invariant(
+            $type instanceof ScalarType || $type instanceof EnumType,
+            'Must be input type'
+        );
+
+        // Scalar/Enum input checks to ensure the type can parse the value to
+        // a non-null value.
+        $parseResult = $type->parseLiteral($valueAST);
+
+        if (null === $parseResult) {
+            $printed = Printer::doPrint($valueAST);
+            return [ "Expected type \"{$type->name}\", found $printed." ];
+        }
+
+        return [];
     }
 
     /**
@@ -205,14 +245,23 @@ class DocumentValidator
      * while maintaining the visitor skip and break API.
      *
      * @param Schema $schema
+     * @param TypeInfo $typeInfo
      * @param Document $documentAST
      * @param array $rules
      * @return array
      */
-    public static function visitUsingRules(Schema $schema, Document $documentAST, array $rules)
+    public static function visitUsingRules(Schema $schema, TypeInfo $typeInfo, Document $documentAST, array $rules)
     {
-        $typeInfo = new TypeInfo($schema);
         $context = new ValidationContext($schema, $documentAST, $typeInfo);
+        $visitors = [];
+        foreach ($rules as $rule) {
+            $visitors[] = $rule($context);
+        }
+        Visitor::visit($documentAST, Visitor::visitWithTypeInfo($typeInfo, Visitor::visitInParallel($visitors)));
+        return $context->getErrors();
+
+
+
         $errors = [];
 
         // TODO: convert to class
@@ -237,7 +286,7 @@ class DocumentValidator
                         if ($node->kind === Node::FRAGMENT_DEFINITION && $key !== null && !empty($instances[$i]['visitSpreadFragments'])) {
                             $result = Visitor::skipNode();
                         } else {
-                            $enter = Visitor::getVisitFn($instances[$i], false, $node->kind);
+                            $enter = Visitor::getVisitFn($instances[$i], $node->kind, false);
                             if ($enter instanceof \Closure) {
                                 // $enter = $enter->bindTo($instances[$i]);
                                 $result = call_user_func_array($enter, func_get_args());
@@ -266,7 +315,7 @@ class DocumentValidator
                         } else if ($result && static::isError($result)) {
                             static::append($errors, $result);
                             for ($j = $i - 1; $j >= 0; $j--) {
-                                $leaveFn = Visitor::getVisitFn($instances[$j], true, $node->kind);
+                                $leaveFn = Visitor::getVisitFn($instances[$j], $node->kind, true);
                                 if ($leaveFn) {
                                     // $leaveFn = $leaveFn->bindTo($instances[$j])
                                     $result = call_user_func_array($leaveFn, func_get_args());
@@ -316,7 +365,7 @@ class DocumentValidator
                             }
                             continue;
                         }
-                        $leaveFn = Visitor::getVisitFn($instances[$i], true, $node->kind);
+                        $leaveFn = Visitor::getVisitFn($instances[$i], $node->kind, true);
 
                         if ($leaveFn) {
                             // $leaveFn = $leaveFn.bindTo($instances[$i]);
diff --git a/src/Validator/Messages.php b/src/Validator/Messages.php
index a8bb5ed..8ff38a4 100644
--- a/src/Validator/Messages.php
+++ b/src/Validator/Messages.php
@@ -1,6 +1,8 @@
 <?php
 namespace GraphQL\Validator;
 
+use GraphQL\Utils;
+
 class Messages
 {
     static function missingArgMessage($fieldName, $argName, $typeName)
@@ -13,23 +15,6 @@ class Messages
         return "Argument $argName expected type $typeName but got: $value.";
     }
 
-    static function defaultForNonNullArgMessage($varName, $typeName, $guessTypeName)
-    {
-        return "Variable \$$varName of type $typeName " .
-        "is required and will never use the default value. " .
-        "Perhaps you meant to use type $guessTypeName.";
-    }
-
-    static function badValueForDefaultArgMessage($varName, $typeName, $value)
-    {
-        return "Variable \$$varName of type $typeName has invalid default value: $value.";
-    }
-
-    static function undefinedFieldMessage($field, $type)
-    {
-        return 'Cannot query field ' . $field . ' on ' . $type;
-    }
-
     static function fragmentOnNonCompositeErrorMessage($fragName, $typeName)
     {
         return "Fragment $fragName cannot condition on non composite type \"$typeName\".";
diff --git a/src/Validator/Rules/ArgumentsOfCorrectType.php b/src/Validator/Rules/ArgumentsOfCorrectType.php
index 8191c03..3f55473 100644
--- a/src/Validator/Rules/ArgumentsOfCorrectType.php
+++ b/src/Validator/Rules/ArgumentsOfCorrectType.php
@@ -16,9 +16,10 @@ use GraphQL\Validator\ValidationContext;
 
 class ArgumentsOfCorrectType
 {
-    static function badValueMessage($argName, $type, $value)
+    static function badValueMessage($argName, $type, $value, $verboseErrors = [])
     {
-        return "Argument \"$argName\" expected type \"$type\" but got: $value.";
+        $message = $verboseErrors ? ("\n" . implode("\n", $verboseErrors)) : '';
+        return "Argument \"$argName\" has invalid value $value.$message";
     }
 
     public function __invoke(ValidationContext $context)
@@ -26,12 +27,17 @@ class ArgumentsOfCorrectType
         return [
             Node::ARGUMENT => function(Argument $argAST) use ($context) {
                 $argDef = $context->getArgument();
-                if ($argDef && !DocumentValidator::isValidLiteralValue($argAST->value, $argDef->getType())) {
-                    return new Error(
-                        self::badValueMessage($argAST->name->value, $argDef->getType(), Printer::doPrint($argAST->value)),
-                        [$argAST->value]
-                    );
+                if ($argDef) {
+                    $errors = DocumentValidator::isValidLiteralValue($argDef->getType(), $argAST->value);
+
+                    if (!empty($errors)) {
+                        $context->reportError(new Error(
+                            self::badValueMessage($argAST->name->value, $argDef->getType(), Printer::doPrint($argAST->value), $errors),
+                            [$argAST->value]
+                        ));
+                    }
                 }
+                return Visitor::skipNode();
             }
         ];
     }
diff --git a/src/Validator/Rules/DefaultValuesOfCorrectType.php b/src/Validator/Rules/DefaultValuesOfCorrectType.php
index 1f29991..22961b7 100644
--- a/src/Validator/Rules/DefaultValuesOfCorrectType.php
+++ b/src/Validator/Rules/DefaultValuesOfCorrectType.php
@@ -13,6 +13,19 @@ use GraphQL\Validator\ValidationContext;
 
 class DefaultValuesOfCorrectType
 {
+    static function badValueForDefaultArgMessage($varName, $type, $value, $verboseErrors = null)
+    {
+        $message = $verboseErrors ? ("\n" . implode("\n", $verboseErrors)) : '';
+        return "Variable \$$varName has invalid default value: $value.$message";
+    }
+
+    static function defaultForNonNullArgMessage($varName, $type, $guessType)
+    {
+        return "Variable \$$varName of type $type " .
+        "is required and will never use the default value. " .
+        "Perhaps you meant to use type $guessType.";
+    }
+
     public function __invoke(ValidationContext $context)
     {
         return [
@@ -22,16 +35,19 @@ class DefaultValuesOfCorrectType
                 $type = $context->getInputType();
 
                 if ($type instanceof NonNull && $defaultValue) {
-                    return new Error(
-                        Messages::defaultForNonNullArgMessage($name, $type, $type->getWrappedType()),
+                    $context->reportError(new Error(
+                        static::defaultForNonNullArgMessage($name, $type, $type->getWrappedType()),
                         [$defaultValue]
-                    );
+                    ));
                 }
-                if ($type && $defaultValue && !DocumentValidator::isValidLiteralValue($defaultValue, $type)) {
-                    return new Error(
-                        Messages::badValueForDefaultArgMessage($name, $type, Printer::doPrint($defaultValue)),
-                        [$defaultValue]
-                    );
+                if ($type && $defaultValue) {
+                    $errors = DocumentValidator::isValidLiteralValue($type, $defaultValue);
+                    if (!empty($errors)) {
+                        $context->reportError(new Error(
+                            static::badValueForDefaultArgMessage($name, $type, Printer::doPrint($defaultValue), $errors),
+                            [$defaultValue]
+                        ));
+                    }
                 }
                 return null;
             }
diff --git a/src/Validator/Rules/FieldsOnCorrectType.php b/src/Validator/Rules/FieldsOnCorrectType.php
index ee91b47..9422388 100644
--- a/src/Validator/Rules/FieldsOnCorrectType.php
+++ b/src/Validator/Rules/FieldsOnCorrectType.php
@@ -5,11 +5,34 @@ namespace GraphQL\Validator\Rules;
 use GraphQL\Error;
 use GraphQL\Language\AST\Field;
 use GraphQL\Language\AST\Node;
+use GraphQL\Schema;
+use GraphQL\Type\Definition\AbstractType;
+use GraphQL\Utils;
 use GraphQL\Validator\Messages;
 use GraphQL\Validator\ValidationContext;
 
 class FieldsOnCorrectType
 {
+    static function undefinedFieldMessage($field, $type, array $suggestedTypes = [])
+    {
+        $message = 'Cannot query field "' . $field . '" on type "' . $type.'".';
+
+        $maxLength = 5;
+        $count = count($suggestedTypes);
+        if ($count > 0) {
+            $suggestions = array_slice($suggestedTypes, 0, $maxLength);
+            $suggestions = Utils::map($suggestions, function($t) { return "\"$t\""; });
+            $suggestions = implode(', ', $suggestions);
+
+            if ($count > $maxLength) {
+                $suggestions .= ', and ' . ($count - $maxLength) . ' other types';
+            }
+            $message .= " However, this field exists on $suggestions.";
+            $message .= ' Perhaps you meant to use an inline fragment?';
+        }
+        return $message;
+    }
+
     public function __invoke(ValidationContext $context)
     {
         return [
@@ -18,13 +41,71 @@ class FieldsOnCorrectType
                 if ($type) {
                     $fieldDef = $context->getFieldDef();
                     if (!$fieldDef) {
-                        return new Error(
-                            Messages::undefinedFieldMessage($node->name->value, $type->name),
+                        // This isn't valid. Let's find suggestions, if any.
+                        $suggestedTypes = [];
+                        if ($type instanceof AbstractType) {
+                            $schema = $context->getSchema();
+                            $suggestedTypes = self::getSiblingInterfacesIncludingField(
+                                $schema,
+                                $type,
+                                $node->name->value
+                            );
+                            $suggestedTypes = array_merge($suggestedTypes,
+                                self::getImplementationsIncludingField($schema, $type, $node->name->value)
+                            );
+                        }
+                        $context->reportError(new Error(
+                            static::undefinedFieldMessage($node->name->value, $type->name, $suggestedTypes),
                             [$node]
-                        );
+                        ));
                     }
                 }
             }
         ];
     }
+
+    /**
+     * Return implementations of `type` that include `fieldName` as a valid field.
+     *
+     * @param Schema $schema
+     * @param AbstractType $type
+     * @param $fieldName
+     * @return array
+     */
+    static function getImplementationsIncludingField(Schema $schema, AbstractType $type, $fieldName)
+    {
+        $types = $schema->getPossibleTypes($type);
+        $types = Utils::filter($types, function($t) use ($fieldName) {return isset($t->getFields()[$fieldName]);});
+        $types = Utils::map($types, function($t) {return $t->name;});
+        sort($types);
+        return $types;
+    }
+
+    /**
+     * Go through all of the implementations of type, and find other interaces
+     * that they implement. If those interfaces include `field` as a valid field,
+     * return them, sorted by how often the implementations include the other
+     * interface.
+     */
+    static function getSiblingInterfacesIncludingField(Schema $schema, AbstractType $type, $fieldName)
+    {
+        $types = $schema->getPossibleTypes($type);
+        $suggestedInterfaces = array_reduce($types, function ($acc, $t) use ($fieldName) {
+            foreach ($t->getInterfaces() as $i) {
+                if (empty($i->getFields()[$fieldName])) {
+                    continue;
+                }
+                if (!isset($acc[$i->name])) {
+                    $acc[$i->name] = 0;
+                }
+                $acc[$i->name] += 1;
+            }
+            return $acc;
+        }, []);
+        $suggestedInterfaceNames = array_keys($suggestedInterfaces);
+        usort($suggestedInterfaceNames, function($a, $b) use ($suggestedInterfaces) {
+            return $suggestedInterfaces[$b] - $suggestedInterfaces[$a];
+        });
+        return $suggestedInterfaceNames;
+    }
 }
diff --git a/src/Validator/Rules/FragmentsOnCompositeTypes.php b/src/Validator/Rules/FragmentsOnCompositeTypes.php
index f3cee89..c9779cd 100644
--- a/src/Validator/Rules/FragmentsOnCompositeTypes.php
+++ b/src/Validator/Rules/FragmentsOnCompositeTypes.php
@@ -30,21 +30,21 @@ class FragmentsOnCompositeTypes
             Node::INLINE_FRAGMENT => function(InlineFragment $node) use ($context) {
                 $type = $context->getType();
 
-                if ($type && !Type::isCompositeType($type)) {
-                    return new Error(
-                        self::inlineFragmentOnNonCompositeErrorMessage($type),
+                if ($node->typeCondition && $type && !Type::isCompositeType($type)) {
+                    $context->reportError(new Error(
+                        static::inlineFragmentOnNonCompositeErrorMessage($type),
                         [$node->typeCondition]
-                    );
+                    ));
                 }
             },
             Node::FRAGMENT_DEFINITION => function(FragmentDefinition $node) use ($context) {
                 $type = $context->getType();
 
                 if ($type && !Type::isCompositeType($type)) {
-                    return new Error(
-                        self::fragmentOnNonCompositeErrorMessage($node->name->value, Printer::doPrint($node->typeCondition)),
+                    $context->reportError(new Error(
+                        static::fragmentOnNonCompositeErrorMessage($node->name->value, Printer::doPrint($node->typeCondition)),
                         [$node->typeCondition]
-                    );
+                    ));
                 }
             }
         ];
diff --git a/src/Validator/Rules/KnownArgumentNames.php b/src/Validator/Rules/KnownArgumentNames.php
index c610573..a6f0ea0 100644
--- a/src/Validator/Rules/KnownArgumentNames.php
+++ b/src/Validator/Rules/KnownArgumentNames.php
@@ -40,10 +40,10 @@ class KnownArgumentNames
                         if (!$fieldArgDef) {
                             $parentType = $context->getParentType();
                             Utils::invariant($parentType);
-                            return new Error(
+                            $context->reportError(new Error(
                                 self::unknownArgMessage($node->name->value, $fieldDef->name, $parentType->name),
                                 [$node]
-                            );
+                            ));
                         }
                     }
                 } else if ($argumentOf->kind === Node::DIRECTIVE) {
@@ -57,10 +57,10 @@ class KnownArgumentNames
                             }
                         }
                         if (!$directiveArgDef) {
-                            return new Error(
+                            $context->reportError(new Error(
                                 self::unknownDirectiveArgMessage($node->name->value, $directive->name),
                                 [$node]
-                            );
+                            ));
                         }
                     }
                 }
diff --git a/src/Validator/Rules/KnownDirectives.php b/src/Validator/Rules/KnownDirectives.php
index da8d3af..8c3ad4b 100644
--- a/src/Validator/Rules/KnownDirectives.php
+++ b/src/Validator/Rules/KnownDirectives.php
@@ -12,6 +12,7 @@ use GraphQL\Language\AST\Node;
 use GraphQL\Language\AST\OperationDefinition;
 use GraphQL\Validator\Messages;
 use GraphQL\Validator\ValidationContext;
+use GraphQL\Type\Definition\Directive as DirectiveDef;
 
 class KnownDirectives
 {
@@ -20,9 +21,9 @@ class KnownDirectives
         return "Unknown directive \"$directiveName\".";
     }
 
-    static function misplacedDirectiveMessage($directiveName, $placement)
+    static function misplacedDirectiveMessage($directiveName, $location)
     {
-        return "Directive \"$directiveName\" may not be used on \"$placement\".";
+        return "Directive \"$directiveName\" may not be used on \"$location\".";
     }
 
     public function __invoke(ValidationContext $context)
@@ -38,39 +39,44 @@ class KnownDirectives
                 }
 
                 if (!$directiveDef) {
-                    return new Error(
+                    $context->reportError(new Error(
                         self::unknownDirectiveMessage($node->name->value),
                         [$node]
-                    );
+                    ));
+                    return ;
                 }
                 $appliedTo = $ancestors[count($ancestors) - 1];
+                $candidateLocation = $this->getLocationForAppliedNode($appliedTo);
 
-                if ($appliedTo instanceof OperationDefinition && !$directiveDef->onOperation) {
-                    return new Error(
-                        self::misplacedDirectiveMessage($node->name->value, 'operation'),
+                if (!$candidateLocation) {
+                    $context->reportError(new Error(
+                        self::misplacedDirectiveMessage($node->name->value, $node->type),
                         [$node]
-                    );
-                }
-                if ($appliedTo instanceof Field && !$directiveDef->onField) {
-                    return new Error(
-                        self::misplacedDirectiveMessage($node->name->value, 'field'),
-                        [$node]
-                    );
-                }
-
-                $fragmentKind = (
-                    $appliedTo instanceof FragmentSpread ||
-                    $appliedTo instanceof InlineFragment ||
-                    $appliedTo instanceof FragmentDefinition
-                );
-
-                if ($fragmentKind && !$directiveDef->onFragment) {
-                    return new Error(
-                        self::misplacedDirectiveMessage($node->name->value, 'fragment'),
-                        [$node]
-                    );
+                    ));
+                } else if (!in_array($candidateLocation, $directiveDef->locations)) {
+                    $context->reportError(new Error(
+                        self::misplacedDirectiveMessage($node->name->value, $candidateLocation),
+                        [ $node ]
+                    ));
                 }
             }
         ];
     }
+
+    private function getLocationForAppliedNode(Node $appliedTo)
+    {
+        switch ($appliedTo->kind) {
+            case Node::OPERATION_DEFINITION:
+                switch ($appliedTo->operation) {
+                    case 'query': return DirectiveDef::$directiveLocations['QUERY'];
+                    case 'mutation': return DirectiveDef::$directiveLocations['MUTATION'];
+                    case 'subscription': return DirectiveDef::$directiveLocations['SUBSCRIPTION'];
+                }
+                break;
+            case Node::FIELD: return DirectiveDef::$directiveLocations['FIELD'];
+            case Node::FRAGMENT_SPREAD: return DirectiveDef::$directiveLocations['FRAGMENT_SPREAD'];
+            case Node::INLINE_FRAGMENT: return DirectiveDef::$directiveLocations['INLINE_FRAGMENT'];
+            case Node::FRAGMENT_DEFINITION: return DirectiveDef::$directiveLocations['FRAGMENT_DEFINITION'];
+        }
+    }
 }
diff --git a/src/Validator/Rules/KnownFragmentNames.php b/src/Validator/Rules/KnownFragmentNames.php
index 3d0dbc8..6361017 100644
--- a/src/Validator/Rules/KnownFragmentNames.php
+++ b/src/Validator/Rules/KnownFragmentNames.php
@@ -21,10 +21,10 @@ class KnownFragmentNames
                 $fragmentName = $node->name->value;
                 $fragment = $context->getFragment($fragmentName);
                 if (!$fragment) {
-                    return new Error(
+                    $context->reportError(new Error(
                         self::unknownFragmentMessage($fragmentName),
                         [$node->name]
-                    );
+                    ));
                 }
             }
         ];
diff --git a/src/Validator/Rules/KnownTypeNames.php b/src/Validator/Rules/KnownTypeNames.php
index 93d5f4c..95f1437 100644
--- a/src/Validator/Rules/KnownTypeNames.php
+++ b/src/Validator/Rules/KnownTypeNames.php
@@ -6,6 +6,7 @@ use GraphQL\Error;
 use GraphQL\Language\AST\Name;
 use GraphQL\Language\AST\NamedType;
 use GraphQL\Language\AST\Node;
+use GraphQL\Language\Visitor;
 use GraphQL\Validator\Messages;
 use GraphQL\Validator\ValidationContext;
 
@@ -18,14 +19,19 @@ class KnownTypeNames
 
     public function __invoke(ValidationContext $context)
     {
+        $skip = function() {return Visitor::skipNode();};
+
         return [
+            Node::OBJECT_TYPE_DEFINITION => $skip,
+            Node::INTERFACE_TYPE_DEFINITION => $skip,
+            Node::UNION_TYPE_DEFINITION => $skip,
+            Node::INPUT_OBJECT_TYPE_DEFINITION => $skip,
+
             Node::NAMED_TYPE => function(NamedType $node, $key) use ($context) {
-                if ($key === 'type' || $key === 'typeCondition') {
-                    $typeName = $node->name->value;
-                    $type = $context->getSchema()->getType($typeName);
-                    if (!$type) {
-                        return new Error(self::unknownTypeMessage($typeName), [$node]);
-                    }
+                $typeName = $node->name->value;
+                $type = $context->getSchema()->getType($typeName);
+                if (!$type) {
+                    $context->reportError(new Error(self::unknownTypeMessage($typeName), [$node]));
                 }
             }
         ];
diff --git a/src/Validator/Rules/LoneAnonymousOperation.php b/src/Validator/Rules/LoneAnonymousOperation.php
new file mode 100644
index 0000000..09d40d8
--- /dev/null
+++ b/src/Validator/Rules/LoneAnonymousOperation.php
@@ -0,0 +1,46 @@
+<?php
+namespace GraphQL\Validator\Rules;
+
+use GraphQL\Error;
+use GraphQL\Language\AST\Document;
+use GraphQL\Language\AST\Node;
+use GraphQL\Language\AST\OperationDefinition;
+use GraphQL\Utils;
+use GraphQL\Validator\ValidationContext;
+
+/**
+ * Lone anonymous operation
+ *
+ * A GraphQL document is only valid if when it contains an anonymous operation
+ * (the query short-hand) that it contains only that one operation definition.
+ */
+class LoneAnonymousOperation extends \PHPUnit_Framework_TestCase
+{
+    static function anonOperationNotAloneMessage()
+    {
+        return 'This anonymous operation must be the only defined operation.';
+    }
+
+    public function __invoke(ValidationContext $context)
+    {
+        $operationCount = 0;
+        return [
+            Node::DOCUMENT => function(Document $node) use (&$operationCount) {
+                $tmp = Utils::filter(
+                    $node->definitions,
+                    function ($definition) {
+                        return $definition->kind === Node::OPERATION_DEFINITION;
+                    }
+                );
+                $operationCount = count($tmp);
+            },
+            Node::OPERATION_DEFINITION => function(OperationDefinition $node) use (&$operationCount, $context) {
+                if (!$node->name && $operationCount > 1) {
+                    $context->reportError(
+                        new Error(self::anonOperationNotAloneMessage(), [$node])
+                    );
+                }
+            }
+        ];
+    }
+}
diff --git a/src/Validator/Rules/NoFragmentCycles.php b/src/Validator/Rules/NoFragmentCycles.php
index 8f41fb8..addf8d7 100644
--- a/src/Validator/Rules/NoFragmentCycles.php
+++ b/src/Validator/Rules/NoFragmentCycles.php
@@ -14,6 +14,7 @@ use GraphQL\Language\AST\FragmentDefinition;
 use GraphQL\Language\AST\FragmentSpread;
 use GraphQL\Language\AST\Node;
 use GraphQL\Language\Visitor;
+use GraphQL\Utils;
 use GraphQL\Validator\ValidationContext;
 
 class NoFragmentCycles
@@ -24,83 +25,86 @@ class NoFragmentCycles
         return "Cannot spread fragment \"$fragName\" within itself$via.";
     }
 
+    public $visitedFrags;
+
+    public $spreadPath;
+
+    public $spreadPathIndexByName;
+
     public function __invoke(ValidationContext $context)
     {
-        // Gather all the fragment spreads ASTs for each fragment definition.
-        // Importantly this does not include inline fragments.
-        $definitions = $context->getDocument()->definitions;
-        $spreadsInFragment = [];
-        foreach ($definitions as $node) {
-            if ($node instanceof FragmentDefinition) {
-                $spreadsInFragment[$node->name->value] = $this->gatherSpreads($node);
-            }
-        }
+        // Tracks already visited fragments to maintain O(N) and to ensure that cycles
+        // are not redundantly reported.
+        $this->visitedFrags = [];
 
-        // Tracks spreads known to lead to cycles to ensure that cycles are not
-        // redundantly reported.
-        $knownToLeadToCycle = new \SplObjectStorage();
+        // Array of AST nodes used to produce meaningful errors
+        $this->spreadPath = [];
+
+        // Position in the spread path
+        $this->spreadPathIndexByName = [];
 
         return [
-            Node::FRAGMENT_DEFINITION => function(FragmentDefinition $node) use ($spreadsInFragment, $knownToLeadToCycle) {
-                $errors = [];
-                $initialName = $node->name->value;
-
-                // Array of AST nodes used to produce meaningful errors
-                $spreadPath = [];
-
-                $this->detectCycleRecursive($initialName, $spreadsInFragment, $knownToLeadToCycle, $initialName, $spreadPath, $errors);
-
-                if (!empty($errors)) {
-                    return $errors;
+            Node::OPERATION_DEFINITION => function () {
+                return Visitor::skipNode();
+            },
+            Node::FRAGMENT_DEFINITION => function (FragmentDefinition $node) use ($context) {
+                if (!isset($this->visitedFrags[$node->name->value])) {
+                    $this->detectCycleRecursive($node, $context);
                 }
+                return Visitor::skipNode();
             }
         ];
     }
 
-    private function detectCycleRecursive($fragmentName, array $spreadsInFragment, \SplObjectStorage $knownToLeadToCycle, $initialName, array &$spreadPath, &$errors)
+    private function detectCycleRecursive(FragmentDefinition $fragment, ValidationContext $context)
     {
-        $spreadNodes = $spreadsInFragment[$fragmentName];
+        $fragmentName = $fragment->name->value;
+        $this->visitedFrags[$fragmentName] = true;
 
-        for ($i = 0; $i < count($spreadNodes); ++$i) {
-            $spreadNode = $spreadNodes[$i];
-            if (isset($knownToLeadToCycle[$spreadNode])) {
-                continue ;
-            }
-            if ($spreadNode->name->value === $initialName) {
-                $cyclePath = array_merge($spreadPath, [$spreadNode]);
-                foreach ($cyclePath as $spread) {
-                    $knownToLeadToCycle[$spread] = true;
-                }
-                $errors[] = new Error(
-                    self::cycleErrorMessage($initialName, array_map(function ($s) {
-                        return $s->name->value;
-                    }, $spreadPath)),
-                    $cyclePath
-                );
-                continue;
-            }
+        $spreadNodes = $context->getFragmentSpreads($fragment);
 
-            foreach ($spreadPath as $spread) {
-                if ($spread === $spreadNode) {
-                    continue 2;
-                }
-            }
-
-            $spreadPath[] = $spreadNode;
-            $this->detectCycleRecursive($spreadNode->name->value, $spreadsInFragment, $knownToLeadToCycle, $initialName, $spreadPath, $errors);
-            array_pop($spreadPath);
+        if (empty($spreadNodes)) {
+            return;
         }
-    }
 
+        $this->spreadPathIndexByName[$fragmentName] = count($this->spreadPath);
 
-    private function gatherSpreads($node)
-    {
-        $spreadNodes = [];
-        Visitor::visit($node, [
-            Node::FRAGMENT_SPREAD => function(FragmentSpread $spread) use (&$spreadNodes) {
-                $spreadNodes[] = $spread;
+        for ($i = 0; $i < count($spreadNodes); $i++) {
+            $spreadNode = $spreadNodes[$i];
+            $spreadName = $spreadNode->name->value;
+            $cycleIndex = isset($this->spreadPathIndexByName[$spreadName]) ? $this->spreadPathIndexByName[$spreadName] : null;
+
+            if ($cycleIndex === null) {
+                $this->spreadPath[] = $spreadNode;
+                if (empty($this->visitedFrags[$spreadName])) {
+                    $spreadFragment = $context->getFragment($spreadName);
+                    if ($spreadFragment) {
+                        $this->detectCycleRecursive($spreadFragment, $context);
+                    }
+                }
+                array_pop($this->spreadPath);
+            } else {
+                $cyclePath = array_slice($this->spreadPath, $cycleIndex);
+                $nodes = $cyclePath;
+
+                if (is_array($spreadNode)) {
+                    $nodes = array_merge($nodes, $spreadNode);
+                } else {
+                    $nodes[] = $spreadNode;
+                }
+
+                $context->reportError(new Error(
+                    self::cycleErrorMessage(
+                        $spreadName,
+                        Utils::map($cyclePath, function ($s) {
+                            return $s->name->value;
+                        })
+                    ),
+                    $nodes
+                ));
             }
-        ]);
-        return $spreadNodes;
+        }
+
+        $this->spreadPathIndexByName[$fragmentName] = null;
     }
 }
diff --git a/src/Validator/Rules/NoUndefinedVariables.php b/src/Validator/Rules/NoUndefinedVariables.php
index dca3ad9..9d7ab5a 100644
--- a/src/Validator/Rules/NoUndefinedVariables.php
+++ b/src/Validator/Rules/NoUndefinedVariables.php
@@ -23,62 +23,43 @@ use GraphQL\Validator\ValidationContext;
  */
 class NoUndefinedVariables
 {
-    static function undefinedVarMessage($varName)
+    static function undefinedVarMessage($varName, $opName = null)
     {
-        return "Variable \"$$varName\" is not defined.";
-    }
-
-    static function undefinedVarByOpMessage($varName, $opName)
-    {
-        return "Variable \"$$varName\" is not defined by operation \"$opName\".";
+        return $opName
+            ? "Variable \"$$varName\" is not defined by operation \"$opName\"."
+            : "Variable \"$$varName\" is not defined.";
     }
 
     public function __invoke(ValidationContext $context)
     {
-        $operation = null;
-        $visitedFragmentNames = [];
-        $definedVariableNames = [];
+        $variableNameDefined = [];
 
         return [
-            // Visit FragmentDefinition after visiting FragmentSpread
-            'visitSpreadFragments' => true,
+            Node::OPERATION_DEFINITION => [
+                'enter' => function() use (&$variableNameDefined) {
+                    $variableNameDefined = [];
+                },
+                'leave' => function(OperationDefinition $operation) use (&$variableNameDefined, $context) {
+                    $usages = $context->getRecursiveVariableUsages($operation);
 
-            Node::OPERATION_DEFINITION => function(OperationDefinition $node, $key, $parent, $path, $ancestors) use (&$operation, &$visitedFragmentNames, &$definedVariableNames) {
-                $operation = $node;
-                $visitedFragmentNames = [];
-                $definedVariableNames = [];
-            },
-            Node::VARIABLE_DEFINITION => function(VariableDefinition $def) use (&$definedVariableNames) {
-                $definedVariableNames[$def->variable->name->value] = true;
-            },
-            Node::VARIABLE => function(Variable $variable, $key, $parent, $path, $ancestors) use (&$definedVariableNames, &$visitedFragmentNames, &$operation) {
-                $varName = $variable->name->value;
-                if (empty($definedVariableNames[$varName])) {
-                    $withinFragment = false;
-                    foreach ($ancestors as $ancestor) {
-                        if ($ancestor instanceof FragmentDefinition) {
-                            $withinFragment = true;
-                            break;
+                    foreach ($usages as $usage) {
+                        $node = $usage['node'];
+                        $varName = $node->name->value;
+
+                        if (empty($variableNameDefined[$varName])) {
+                            $context->reportError(new Error(
+                                self::undefinedVarMessage(
+                                    $varName,
+                                    $operation->name ? $operation->name->value : null
+                                ),
+                                [ $node, $operation ]
+                            ));
                         }
                     }
-                    if ($withinFragment && $operation && $operation->name) {
-                        return new Error(
-                            self::undefinedVarByOpMessage($varName, $operation->name->value),
-                            [$variable, $operation]
-                        );
-                    }
-                    return new Error(
-                        self::undefinedVarMessage($varName),
-                        [$variable]
-                    );
                 }
-            },
-            Node::FRAGMENT_SPREAD => function(FragmentSpread $spreadAST) use (&$visitedFragmentNames) {
-                // Only visit fragments of a particular name once per operation
-                if (!empty($visitedFragmentNames[$spreadAST->name->value])) {
-                    return Visitor::skipNode();
-                }
-                $visitedFragmentNames[$spreadAST->name->value] = true;
+            ],
+            Node::VARIABLE_DEFINITION => function(VariableDefinition $def) use (&$variableNameDefined) {
+                $variableNameDefined[$def->variable->name->value] = true;
             }
         ];
     }
diff --git a/src/Validator/Rules/NoUnusedFragments.php b/src/Validator/Rules/NoUnusedFragments.php
index bea8422..bf88240 100644
--- a/src/Validator/Rules/NoUnusedFragments.php
+++ b/src/Validator/Rules/NoUnusedFragments.php
@@ -6,6 +6,7 @@ use GraphQL\Error;
 use GraphQL\Language\AST\FragmentDefinition;
 use GraphQL\Language\AST\FragmentSpread;
 use GraphQL\Language\AST\Node;
+use GraphQL\Language\Visitor;
 use GraphQL\Validator\Messages;
 use GraphQL\Validator\ValidationContext;
 
@@ -16,63 +17,45 @@ class NoUnusedFragments
         return "Fragment \"$fragName\" is never used.";
     }
 
+    public $operationDefs;
+
+    public $fragmentDefs;
+
     public function __invoke(ValidationContext $context)
     {
-        $fragmentDefs = [];
-        $spreadsWithinOperation = [];
-        $fragAdjacencies = new \stdClass();
-        $spreadNames = new \stdClass();
+        $this->operationDefs = [];
+        $this->fragmentDefs = [];
 
         return [
-            Node::OPERATION_DEFINITION => function() use (&$spreadNames, &$spreadsWithinOperation) {
-                $spreadNames = new \stdClass();
-                $spreadsWithinOperation[] = $spreadNames;
+            Node::OPERATION_DEFINITION => function($node) {
+                $this->operationDefs[] = $node;
+                return Visitor::skipNode();
             },
-            Node::FRAGMENT_DEFINITION => function(FragmentDefinition $def) use (&$fragmentDefs, &$spreadNames, &$fragAdjacencies) {
-                $fragmentDefs[] = $def;
-                $spreadNames = new \stdClass();
-                $fragAdjacencies->{$def->name->value} = $spreadNames;
-            },
-            Node::FRAGMENT_SPREAD => function(FragmentSpread $spread) use (&$spreadNames) {
-                $spreadNames->{$spread->name->value} = true;
+            Node::FRAGMENT_DEFINITION => function(FragmentDefinition $def) {
+                $this->fragmentDefs[] = $def;
+                return Visitor::skipNode();
             },
             Node::DOCUMENT => [
-                'leave' => function() use (&$fragAdjacencies, &$spreadsWithinOperation, &$fragmentDefs) {
+                'leave' => function() use ($context) {
                     $fragmentNameUsed = [];
 
-                    foreach ($spreadsWithinOperation as $spreads) {
-                        $this->reduceSpreadFragments($spreads, $fragmentNameUsed, $fragAdjacencies);
-                    }
-
-                    $errors = [];
-                    foreach ($fragmentDefs as $def) {
-                        if (empty($fragmentNameUsed[$def->name->value])) {
-                            $errors[] = new Error(
-                                self::unusedFragMessage($def->name->value),
-                                [$def]
-                            );
+                    foreach ($this->operationDefs as $operation) {
+                        foreach ($context->getRecursivelyReferencedFragments($operation) as $fragment) {
+                            $fragmentNameUsed[$fragment->name->value] = true;
+                        }
+                    }
+
+                    foreach ($this->fragmentDefs as $fragmentDef) {
+                        $fragName = $fragmentDef->name->value;
+                        if (empty($fragmentNameUsed[$fragName])) {
+                            $context->reportError(new Error(
+                                self::unusedFragMessage($fragName),
+                                [ $fragmentDef ]
+                            ));
                         }
                     }
-                    return !empty($errors) ? $errors : null;
                 }
             ]
         ];
     }
-
-    private function reduceSpreadFragments($spreads, &$fragmentNameUsed, &$fragAdjacencies)
-    {
-        foreach ($spreads as $fragName => $fragment) {
-            if (empty($fragmentNameUsed[$fragName])) {
-                $fragmentNameUsed[$fragName] = true;
-
-                if (isset($fragAdjacencies->{$fragName})) {
-                    $this->reduceSpreadFragments(
-                        $fragAdjacencies->{$fragName},
-                        $fragmentNameUsed,
-                        $fragAdjacencies
-                    );
-                }
-            }
-        }
-    }
 }
diff --git a/src/Validator/Rules/OverlappingFieldsCanBeMerged.php b/src/Validator/Rules/OverlappingFieldsCanBeMerged.php
index fb27759..f9194ac 100644
--- a/src/Validator/Rules/OverlappingFieldsCanBeMerged.php
+++ b/src/Validator/Rules/OverlappingFieldsCanBeMerged.php
@@ -54,18 +54,15 @@ class OverlappingFieldsCanBeMerged
 
                     $conflicts = $this->findConflicts($fieldMap, $context, $comparedSet);
 
-                    if (!empty($conflicts)) {
-                        return array_map(function ($conflict) {
-                            $responseName = $conflict[0][0];
-                            $reason = $conflict[0][1];
-                            $fields = $conflict[1];
-
-                            return new Error(
-                                self::fieldsConflictMessage($responseName, $reason),
-                                $fields
-                            );
-                        }, $conflicts);
+                    foreach ($conflicts as $conflict) {
+                        $responseName = $conflict[0][0];
+                        $reason = $conflict[0][1];
+                        $fields = $conflict[1];
 
+                        $context->reportError(new Error(
+                            self::fieldsConflictMessage($responseName, $reason),
+                            $fields
+                        ));
                     }
                 }
             ]
diff --git a/src/Validator/Rules/PossibleFragmentSpreads.php b/src/Validator/Rules/PossibleFragmentSpreads.php
index e4fcce0..2062138 100644
--- a/src/Validator/Rules/PossibleFragmentSpreads.php
+++ b/src/Validator/Rules/PossibleFragmentSpreads.php
@@ -32,10 +32,10 @@ class PossibleFragmentSpreads
                 $fragType = Type::getNamedType($context->getType());
                 $parentType = $context->getParentType();
                 if ($fragType && $parentType && !$this->doTypesOverlap($fragType, $parentType)) {
-                    return new Error(
+                    $context->reportError(new Error(
                         self::typeIncompatibleAnonSpreadMessage($parentType, $fragType),
                         [$node]
-                    );
+                    ));
                 }
             },
             Node::FRAGMENT_SPREAD => function(FragmentSpread $node) use ($context) {
@@ -44,10 +44,10 @@ class PossibleFragmentSpreads
                 $parentType = $context->getParentType();
 
                 if ($fragType && $parentType && !$this->doTypesOverlap($fragType, $parentType)) {
-                    return new Error(
+                    $context->reportError(new Error(
                         self::typeIncompatibleSpreadMessage($fragName, $parentType, $fragType),
                         [$node]
-                    );
+                    ));
                 }
             }
         ];
diff --git a/src/Validator/Rules/ProvidedNonNullArguments.php b/src/Validator/Rules/ProvidedNonNullArguments.php
index f8595a0..1cdc7fc 100644
--- a/src/Validator/Rules/ProvidedNonNullArguments.php
+++ b/src/Validator/Rules/ProvidedNonNullArguments.php
@@ -33,7 +33,6 @@ class ProvidedNonNullArguments
                     if (!$fieldDef) {
                         return Visitor::skipNode();
                     }
-                    $errors = [];
                     $argASTs = $fieldAST->arguments ?: [];
 
                     $argASTMap = [];
@@ -43,16 +42,12 @@ class ProvidedNonNullArguments
                     foreach ($fieldDef->args as $argDef) {
                         $argAST = isset($argASTMap[$argDef->name]) ? $argASTMap[$argDef->name] : null;
                         if (!$argAST && $argDef->getType() instanceof NonNull) {
-                            $errors[] = new Error(
+                            $context->reportError(new Error(
                                 self::missingFieldArgMessage($fieldAST->name->value, $argDef->name, $argDef->getType()),
                                 [$fieldAST]
-                            );
+                            ));
                         }
                     }
-
-                    if (!empty($errors)) {
-                        return $errors;
-                    }
                 }
             ],
             Node::DIRECTIVE => [
@@ -61,7 +56,6 @@ class ProvidedNonNullArguments
                     if (!$directiveDef) {
                         return Visitor::skipNode();
                     }
-                    $errors = [];
                     $argASTs = $directiveAST->arguments ?: [];
                     $argASTMap = [];
                     foreach ($argASTs as $argAST) {
@@ -71,15 +65,12 @@ class ProvidedNonNullArguments
                     foreach ($directiveDef->args as $argDef) {
                         $argAST = isset($argASTMap[$argDef->name]) ? $argASTMap[$argDef->name] : null;
                         if (!$argAST && $argDef->getType() instanceof NonNull) {
-                            $errors[] = new Error(
+                            $context->reportError(new Error(
                                 self::missingDirectiveArgMessage($directiveAST->name->value, $argDef->name, $argDef->getType()),
                                 [$directiveAST]
-                            );
+                            ));
                         }
                     }
-                    if (!empty($errors)) {
-                        return $errors;
-                    }
                 }
             ]
         ];
diff --git a/src/Validator/Rules/ScalarLeafs.php b/src/Validator/Rules/ScalarLeafs.php
index 58238bd..f782af2 100644
--- a/src/Validator/Rules/ScalarLeafs.php
+++ b/src/Validator/Rules/ScalarLeafs.php
@@ -29,16 +29,16 @@ class ScalarLeafs
                 if ($type) {
                     if (Type::isLeafType($type)) {
                         if ($node->selectionSet) {
-                            return new Error(
+                            $context->reportError(new Error(
                                 self::noSubselectionAllowedMessage($node->name->value, $type),
                                 [$node->selectionSet]
-                            );
+                            ));
                         }
                     } else if (!$node->selectionSet) {
-                        return new Error(
+                        $context->reportError(new Error(
                             self::requiredSubselectionMessage($node->name->value, $type),
                             [$node]
-                        );
+                        ));
                     }
                 }
             }
diff --git a/src/Validator/Rules/VariablesAreInputTypes.php b/src/Validator/Rules/VariablesAreInputTypes.php
index faca0ce..edc8c8f 100644
--- a/src/Validator/Rules/VariablesAreInputTypes.php
+++ b/src/Validator/Rules/VariablesAreInputTypes.php
@@ -27,10 +27,10 @@ class VariablesAreInputTypes
                 // If the variable type is not an input type, return an error.
                 if ($type && !Type::isInputType($type)) {
                     $variableName = $node->variable->name->value;
-                    return new Error(
+                    $context->reportError(new Error(
                         self::nonInputTypeOnVarMessage($variableName, Printer::doPrint($node->type)),
                         [ $node->type ]
-                    );
+                    ));
                 }
             }
         ];
diff --git a/src/Validator/Rules/VariablesInAllowedPosition.php b/src/Validator/Rules/VariablesInAllowedPosition.php
index ad6ccd7..9693161 100644
--- a/src/Validator/Rules/VariablesInAllowedPosition.php
+++ b/src/Validator/Rules/VariablesInAllowedPosition.php
@@ -47,10 +47,10 @@ class VariablesInAllowedPosition
                 if ($varType && $inputType &&
                     !$this->varTypeAllowedForType($this->effectiveType($varType, $varDef), $inputType)
                 ) {
-                    return new Error(
+                    $context->reportError(new Error(
                         Messages::badVarPosMessage($varName, $varType, $inputType),
                         [$variableAST]
-                    );
+                    ));
                 }
             }
         ];
diff --git a/src/Validator/ValidationContext.php b/src/Validator/ValidationContext.php
index 27d56f1..ed2b4b0 100644
--- a/src/Validator/ValidationContext.php
+++ b/src/Validator/ValidationContext.php
@@ -1,5 +1,13 @@
 <?php
 namespace GraphQL\Validator;
+
+use GraphQL\Language\AST\FragmentSpread;
+use GraphQL\Language\AST\HasSelectionSet;
+use GraphQL\Language\AST\OperationDefinition;
+use GraphQL\Language\AST\Variable;
+use GraphQL\Language\Visitor;
+use \SplObjectStorage;
+use GraphQL\Error;
 use GraphQL\Schema;
 use GraphQL\Language\AST\Document;
 use GraphQL\Language\AST\FragmentDefinition;
@@ -33,16 +41,69 @@ class ValidationContext
      */
     private $_typeInfo;
 
+    /**
+     * @var Error[]
+     */
+    private $_errors;
+
     /**
      * @var array<string, FragmentDefinition>
      */
     private $_fragments;
 
+    /**
+     * @var SplObjectStorage
+     */
+    private $_fragmentSpreads;
+
+    /**
+     * @var SplObjectStorage
+     */
+    private $_recursivelyReferencedFragments;
+
+    /**
+     * @var SplObjectStorage
+     */
+    private $_variableUsages;
+
+    /**
+     * @var SplObjectStorage
+     */
+    private $_recursiveVariableUsages;
+
+    /**
+     * ValidationContext constructor.
+     *
+     * @param Schema $schema
+     * @param Document $ast
+     * @param TypeInfo $typeInfo
+     */
     function __construct(Schema $schema, Document $ast, TypeInfo $typeInfo)
     {
         $this->_schema = $schema;
         $this->_ast = $ast;
         $this->_typeInfo = $typeInfo;
+        $this->_errors = [];
+        $this->_fragmentSpreads = new SplObjectStorage();
+        $this->_recursivelyReferencedFragments = new SplObjectStorage();
+        $this->_variableUsages = new SplObjectStorage();
+        $this->_recursiveVariableUsages = new SplObjectStorage();
+    }
+
+    /**
+     * @param Error $error
+     */
+    function reportError(Error $error)
+    {
+        $this->_errors[] = $error;
+    }
+
+    /**
+     * @return Error[]
+     */
+    function getErrors()
+    {
+        return $this->_errors;
     }
 
     /**
@@ -80,6 +141,113 @@ class ValidationContext
         return isset($fragments[$name]) ? $fragments[$name] : null;
     }
 
+    /**
+     * @param HasSelectionSet $node
+     * @return FragmentSpread[]
+     */
+    function getFragmentSpreads(HasSelectionSet $node)
+    {
+        $spreads = isset($this->_fragmentSpreads[$node]) ? $this->_fragmentSpreads[$node] : null;
+        if (!$spreads) {
+            $spreads = [];
+            $setsToVisit = [$node->selectionSet];
+            while (!empty($setsToVisit)) {
+                $set = array_pop($setsToVisit);
+
+                for ($i = 0; $i < count($set->selections); $i++) {
+                    $selection = $set->selections[$i];
+                    if ($selection->kind === Node::FRAGMENT_SPREAD) {
+                        $spreads[] = $selection;
+                    } else if ($selection->selectionSet) {
+                        $setsToVisit[] = $selection->selectionSet;
+                    }
+                }
+            }
+            $this->_fragmentSpreads[$node] = $spreads;
+        }
+        return $spreads;
+    }
+
+    /**
+     * @param OperationDefinition $operation
+     * @return FragmentDefinition[]
+     */
+    function getRecursivelyReferencedFragments(OperationDefinition $operation)
+    {
+        $fragments = isset($this->_recursivelyReferencedFragments[$operation]) ? $this->_recursivelyReferencedFragments[$operation] : null;
+
+        if (!$fragments) {
+            $fragments = [];
+            $collectedNames = [];
+            $nodesToVisit = [$operation];
+            while (!empty($nodesToVisit)) {
+                $node = array_pop($nodesToVisit);
+                $spreads = $this->getFragmentSpreads($node);
+                for ($i = 0; $i < count($spreads); $i++) {
+                    $fragName = $spreads[$i]->name->value;
+
+                    if (empty($collectedNames[$fragName])) {
+                        $collectedNames[$fragName] = true;
+                        $fragment = $this->getFragment($fragName);
+                        if ($fragment) {
+                            $fragments[] = $fragment;
+                            $nodesToVisit[] = $fragment;
+                        }
+                    }
+                }
+            }
+            $this->_recursivelyReferencedFragments[$operation] = $fragments;
+        }
+        return $fragments;
+    }
+
+    /**
+     * @param HasSelectionSet $node
+     * @return array List of ['node' => Variable, 'type' => ?InputObjectType]
+     */
+    function getVariableUsages(HasSelectionSet $node)
+    {
+        $usages = isset($this->_variableUsages[$node]) ? $this->_variableUsages[$node] : null;
+
+        if (!$usages) {
+            $newUsages = [];
+            $typeInfo = new TypeInfo($this->_schema);
+            Visitor::visit($node, Visitor::visitWithTypeInfo($typeInfo, [
+                Node::VARIABLE_DEFINITION => function () {
+                    return false;
+                },
+                Node::VARIABLE => function (Variable $variable) use (&$newUsages, $typeInfo) {
+                    $newUsages[] = ['node' => $variable, 'type' => $typeInfo->getInputType()];
+                }
+            ]));
+            $usages = $newUsages;
+            $this->_variableUsages[$node] = $usages;
+        }
+        return $usages;
+    }
+
+    /**
+     * @param OperationDefinition $operation
+     * @return array List of ['node' => Variable, 'type' => ?InputObjectType]
+     */
+    function getRecursiveVariableUsages(OperationDefinition $operation)
+    {
+        $usages = isset($this->_recursiveVariableUsages[$operation]) ? $this->_recursiveVariableUsages[$operation] : null;
+
+        if (!$usages) {
+            $usages = $this->getVariableUsages($operation);
+            $fragments = $this->getRecursivelyReferencedFragments($operation);
+
+            $tmp = [$usages];
+            for ($i = 0; $i < count($fragments); $i++) {
+                $tmp[] = $this->getVariableUsages($fragments[$i]);
+            }
+            $usages = call_user_func_array('array_merge', $tmp);
+            $this->_recursiveVariableUsages[$operation] = $usages;
+        }
+        return $usages;
+    }
+
     /**
      * Returns OutputType
      *
diff --git a/tests/Validator/ArgumentsOfCorrectTypeTest.php b/tests/Validator/ArgumentsOfCorrectTypeTest.php
index 577be7c..f53d14a 100644
--- a/tests/Validator/ArgumentsOfCorrectTypeTest.php
+++ b/tests/Validator/ArgumentsOfCorrectTypeTest.php
@@ -7,25 +7,22 @@ use GraphQL\Validator\Rules\ArgumentsOfCorrectType;
 
 class ArgumentsOfCorrectTypeTest extends TestCase
 {
-    function missingArg($fieldName, $argName, $typeName, $line, $column)
+    function badValue($argName, $typeName, $value, $line, $column, $errors = null)
     {
-        return FormattedError::create(
-            Messages::missingArgMessage($fieldName, $argName, $typeName),
-            [new SourceLocation($line, $column)]
-        );
-    }
+        $realErrors = !$errors ? ["Expected type \"$typeName\", found $value."] : $errors;
 
-    function badValue($argName, $typeName, $value, $line, $column)
-    {
         return FormattedError::create(
-            ArgumentsOfCorrectType::badValueMessage($argName, $typeName, $value),
+            ArgumentsOfCorrectType::badValueMessage($argName, $typeName, $value, $realErrors),
             [new SourceLocation($line, $column)]
         );
     }
 
     // Validate: Argument values of correct type
-    // Valid values:
+    // Valid values
 
+    /**
+     * @it Good int value
+     */
     public function testGoodIntValue()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType(), '
@@ -37,6 +34,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it Good boolean value
+     */
     public function testGoodBooleanValue()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType(), '
@@ -48,6 +48,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
       ');
     }
 
+    /**
+     * @it Good string value
+     */
     public function testGoodStringValue()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType(), '
@@ -59,6 +62,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it Good float value
+     */
     public function testGoodFloatValue()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType(), '
@@ -70,6 +76,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it Int into Float
+     */
     public function testIntIntoFloat()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType(), '
@@ -81,6 +90,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it Int into ID
+     */
     public function testIntIntoID()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType(), '
@@ -92,6 +104,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it String into ID
+     */
     public function testStringIntoID()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType(), '
@@ -103,6 +118,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it Good enum value
+     */
     public function testGoodEnumValue()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType(), '
@@ -115,6 +133,10 @@ class ArgumentsOfCorrectTypeTest extends TestCase
     }
 
     // Invalid String values
+
+    /**
+     * @it Int into String
+     */
     public function testIntIntoString()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -128,6 +150,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ]);
     }
 
+    /**
+     * @it Float into String
+     */
     public function testFloatIntoString()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -141,6 +166,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ]);
     }
 
+    /**
+     * @it Boolean into String
+     */
     public function testBooleanIntoString()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -154,6 +182,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ]);
     }
 
+    /**
+     * @it Unquoted String into String
+     */
     public function testUnquotedStringIntoString()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -168,6 +199,10 @@ class ArgumentsOfCorrectTypeTest extends TestCase
     }
 
     // Invalid Int values
+
+    /**
+     * @it String into Int
+     */
     public function testStringIntoInt()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -181,6 +216,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ]);
     }
 
+    /**
+     * @it Big Int into Int
+     */
     public function testBigIntIntoInt()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -194,6 +232,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ]);
     }
 
+    /**
+     * @it Unquoted String into Int
+     */
     public function testUnquotedStringIntoInt()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -207,6 +248,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ]);
     }
 
+    /**
+     * @it Simple Float into Int
+     */
     public function testSimpleFloatIntoInt()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -220,6 +264,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ]);
     }
 
+    /**
+     * @it Float into Int
+     */
     public function testFloatIntoInt()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -234,6 +281,10 @@ class ArgumentsOfCorrectTypeTest extends TestCase
     }
 
     // Invalid Float values
+
+    /**
+     * @it String into Float
+     */
     public function testStringIntoFloat()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -247,6 +298,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ]);
     }
 
+    /**
+     * @it Boolean into Float
+     */
     public function testBooleanIntoFloat()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -260,6 +314,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ]);
     }
 
+    /**
+     * @it Unquoted into Float
+     */
     public function testUnquotedIntoFloat()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -274,6 +331,10 @@ class ArgumentsOfCorrectTypeTest extends TestCase
     }
 
     // Invalid Boolean value
+
+    /**
+     * @it Int into Boolean
+     */
     public function testIntIntoBoolean()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -287,6 +348,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ]);
     }
 
+    /**
+     * @it Float into Boolean
+     */
     public function testFloatIntoBoolean()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -300,6 +364,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ]);
     }
 
+    /**
+     * @it String into Boolean
+     */
     public function testStringIntoBoolean()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -313,6 +380,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ]);
     }
 
+    /**
+     * @it Unquoted into Boolean
+     */
     public function testUnquotedIntoBoolean()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -327,6 +397,10 @@ class ArgumentsOfCorrectTypeTest extends TestCase
     }
 
     // Invalid ID value
+
+    /**
+     * @it Float into ID
+     */
     public function testFloatIntoID()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -340,6 +414,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ]);
     }
 
+    /**
+     * @it Boolean into ID
+     */
     public function testBooleanIntoID()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -353,6 +430,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ]);
     }
 
+    /**
+     * @it Unquoted into ID
+     */
     public function testUnquotedIntoID()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -367,6 +447,10 @@ class ArgumentsOfCorrectTypeTest extends TestCase
     }
 
     // Invalid Enum value
+
+    /**
+     * @it Int into Enum
+     */
     public function testIntIntoEnum()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -380,6 +464,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ]);
     }
 
+    /**
+     * @it Float into Enum
+     */
     public function testFloatIntoEnum()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -393,6 +480,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ]);
     }
 
+    /**
+     * @it String into Enum
+     */
     public function testStringIntoEnum()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -406,6 +496,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ]);
     }
 
+    /**
+     * @it Boolean into Enum
+     */
     public function testBooleanIntoEnum()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -419,6 +512,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ]);
     }
 
+    /**
+     * @it Unknown Enum Value into Enum
+     */
     public function testUnknownEnumValueIntoEnum()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -432,6 +528,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ]);
     }
 
+    /**
+     * @it Different case Enum Value into Enum
+     */
     public function testDifferentCaseEnumValueIntoEnum()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -446,6 +545,10 @@ class ArgumentsOfCorrectTypeTest extends TestCase
     }
 
     // Valid List value
+
+    /**
+     * @it Good list value
+     */
     public function testGoodListValue()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType(), '
@@ -457,6 +560,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it Empty list value
+     */
     public function testEmptyListValue()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType(), '
@@ -468,6 +574,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it Single value into List
+     */
     public function testSingleValueIntoList()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType(), '
@@ -480,6 +589,10 @@ class ArgumentsOfCorrectTypeTest extends TestCase
     }
 
     // Invalid List value
+
+    /**
+     * @it Incorrect item type
+     */
     public function testIncorrectItemtype()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -489,10 +602,15 @@ class ArgumentsOfCorrectTypeTest extends TestCase
           }
         }
         ', [
-            $this->badValue('stringListArg', '[String]', '["one", 2]', 4, 47),
+            $this->badValue('stringListArg', '[String]', '["one", 2]', 4, 47, [
+                'In element #1: Expected type "String", found 2.'
+            ]),
         ]);
     }
 
+    /**
+     * @it Single value of incorrect type
+     */
     public function testSingleValueOfIncorrectType()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType(), '
@@ -502,11 +620,15 @@ class ArgumentsOfCorrectTypeTest extends TestCase
           }
         }
         ', [
-            $this->badValue('stringListArg', '[String]', '1', 4, 47),
+            $this->badValue('stringListArg', 'String', '1', 4, 47),
         ]);
     }
 
     // Valid non-nullable value
+
+    /**
+     * @it Arg on optional arg
+     */
     public function testArgOnOptionalArg()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType(), '
@@ -518,6 +640,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it No Arg on optional arg
+     */
     public function testNoArgOnOptionalArg()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType(), '
@@ -529,6 +654,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it Multiple args
+     */
     public function testMultipleArgs()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType(), '
@@ -540,6 +668,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it Multiple args reverse order
+     */
     public function testMultipleArgsReverseOrder()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType(), '
@@ -551,6 +682,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it No args on multiple optional
+     */
     public function testNoArgsOnMultipleOptional()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType(), '
@@ -562,6 +696,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it One arg on multiple optional
+     */
     public function testOneArgOnMultipleOptional()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType, '
@@ -573,6 +710,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it Second arg on multiple optional
+     */
     public function testSecondArgOnMultipleOptional()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType, '
@@ -584,6 +724,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it Multiple reqs on mixedList
+     */
     public function testMultipleReqsOnMixedList()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType, '
@@ -595,6 +738,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it Multiple reqs and one opt on mixedList
+     */
     public function testMultipleReqsAndOneOptOnMixedList()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType, '
@@ -606,6 +752,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it All reqs and opts on mixedList
+     */
     public function testAllReqsAndOptsOnMixedList()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType, '
@@ -618,6 +767,10 @@ class ArgumentsOfCorrectTypeTest extends TestCase
     }
 
     // Invalid non-nullable value
+
+    /**
+     * @it Incorrect value type
+     */
     public function testIncorrectValueType()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType, '
@@ -627,11 +780,14 @@ class ArgumentsOfCorrectTypeTest extends TestCase
           }
         }
         ', [
-            $this->badValue('req2', 'Int!', '"two"', 4, 32),
-            $this->badValue('req1', 'Int!', '"one"', 4, 45),
+            $this->badValue('req2', 'Int', '"two"', 4, 32),
+            $this->badValue('req1', 'Int', '"one"', 4, 45),
         ]);
     }
 
+    /**
+     * @it Incorrect value and missing argument
+     */
     public function testIncorrectValueAndMissingArgument()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType, '
@@ -641,12 +797,16 @@ class ArgumentsOfCorrectTypeTest extends TestCase
           }
         }
         ', [
-            $this->badValue('req1', 'Int!', '"one"', 4, 32),
+            $this->badValue('req1', 'Int', '"one"', 4, 32),
         ]);
     }
 
 
     // Valid input object value
+
+    /**
+     * @it Optional arg, despite required field in type
+     */
     public function testOptionalArgDespiteRequiredFieldInType()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType, '
@@ -658,6 +818,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it Partial object, only required
+     */
     public function testPartialObjectOnlyRequired()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType, '
@@ -669,6 +832,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it Partial object, required field can be falsey
+     */
     public function testPartialObjectRequiredFieldCanBeFalsey()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType, '
@@ -680,6 +846,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it Partial object, including required
+     */
     public function testPartialObjectIncludingRequired()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType, '
@@ -691,6 +860,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it Full object
+     */
     public function testFullObject()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType, '
@@ -708,6 +880,9 @@ class ArgumentsOfCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it Full object with fields in different order
+     */
     public function testFullObjectWithFieldsInDifferentOrder()
     {
         $this->expectPassesRule(new ArgumentsOfCorrectType(), '
@@ -726,6 +901,10 @@ class ArgumentsOfCorrectTypeTest extends TestCase
     }
 
     // Invalid input object value
+
+    /**
+     * @it Partial object, missing required
+     */
     public function testPartialObjectMissingRequired()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType, '
@@ -735,10 +914,15 @@ class ArgumentsOfCorrectTypeTest extends TestCase
           }
         }
         ', [
-            $this->badValue('complexArg', 'ComplexInput', '{intField: 4}', 4, 41),
+            $this->badValue('complexArg', 'ComplexInput', '{intField: 4}', 4, 41, [
+                'In field "requiredField": Expected "Boolean!", found null.'
+            ]),
         ]);
     }
 
+    /**
+     * @it Partial object, invalid field type
+     */
     public function testPartialObjectInvalidFieldType()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType, '
@@ -756,11 +940,15 @@ class ArgumentsOfCorrectTypeTest extends TestCase
                 'ComplexInput',
                 '{stringListField: ["one", 2], requiredField: true}',
                 4,
-                41
+                41,
+                [ 'In field "stringListField": In element #1: Expected type "String", found 2.' ]
             ),
         ]);
     }
 
+    /**
+     * @it Partial object, unknown field arg
+     */
     public function testPartialObjectUnknownFieldArg()
     {
         $this->expectFailsRule(new ArgumentsOfCorrectType, '
@@ -778,8 +966,45 @@ class ArgumentsOfCorrectTypeTest extends TestCase
                 'ComplexInput',
                 '{requiredField: true, unknownField: "value"}',
                 4,
-                41
+                41,
+                [ 'In field "unknownField": Unknown field.' ]
             ),
         ]);
     }
+
+    // Directive arguments
+
+    /**
+     * @it with directives of valid types
+     */
+    public function testWithDirectivesOfValidTypes()
+    {
+        $this->expectPassesRule(new ArgumentsOfCorrectType(), '
+        {
+          dog @include(if: true) {
+            name
+          }
+          human @skip(if: false) {
+            name
+          }
+        }
+      ');
+    }
+
+    /**
+     * @it with directive with incorrect types
+     */
+    public function testWithDirectiveWithIncorrectTypes()
+    {
+        $this->expectFailsRule(new ArgumentsOfCorrectType, '
+        {
+          dog @include(if: "yes") {
+            name @skip(if: ENUM)
+          }
+        }
+      ', [
+            $this->badValue('if', 'Boolean', '"yes"', 3, 28),
+            $this->badValue('if', 'Boolean', 'ENUM', 4, 28),
+        ]);
+    }
 }
diff --git a/tests/Validator/DefaultValuesOfCorrectTypeTest.php b/tests/Validator/DefaultValuesOfCorrectTypeTest.php
index f48de76..a979cdd 100644
--- a/tests/Validator/DefaultValuesOfCorrectTypeTest.php
+++ b/tests/Validator/DefaultValuesOfCorrectTypeTest.php
@@ -10,6 +10,9 @@ class DefaultValuesOfCorrectTypeTest extends TestCase
 {
     // Validate: Variable default values of correct type
 
+    /**
+     * @it variables with no default values
+     */
     public function testVariablesWithNoDefaultValues()
     {
         $this->expectPassesRule(new DefaultValuesOfCorrectType, '
@@ -19,6 +22,9 @@ class DefaultValuesOfCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it required variables without default values
+     */
     public function testRequiredVariablesWithoutDefaultValues()
     {
         $this->expectPassesRule(new DefaultValuesOfCorrectType, '
@@ -28,6 +34,9 @@ class DefaultValuesOfCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it variables with valid default values
+     */
     public function testVariablesWithValidDefaultValues()
     {
         $this->expectPassesRule(new DefaultValuesOfCorrectType, '
@@ -41,6 +50,9 @@ class DefaultValuesOfCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it no required variables with default values
+     */
     public function testNoRequiredVariablesWithDefaultValues()
     {
         $this->expectFailsRule(new DefaultValuesOfCorrectType, '
@@ -53,6 +65,9 @@ class DefaultValuesOfCorrectTypeTest extends TestCase
         ]);
     }
 
+    /**
+     * @it variables with invalid default values
+     */
     public function testVariablesWithInvalidDefaultValues()
     {
         $this->expectFailsRule(new DefaultValuesOfCorrectType, '
@@ -64,12 +79,21 @@ class DefaultValuesOfCorrectTypeTest extends TestCase
         dog { name }
       }
         ', [
-            $this->badValue('a', 'Int', '"one"', 3, 19),
-            $this->badValue('b', 'String', '4', 4, 22),
-            $this->badValue('c', 'ComplexInput', '"notverycomplex"', 5, 28)
+            $this->badValue('a', 'Int', '"one"', 3, 19, [
+                'Expected type "Int", found "one".'
+            ]),
+            $this->badValue('b', 'String', '4', 4, 22, [
+                'Expected type "String", found 4.'
+            ]),
+            $this->badValue('c', 'ComplexInput', '"notverycomplex"', 5, 28, [
+                'Expected "ComplexInput", found not an object.'
+            ])
         ]);
     }
 
+    /**
+     * @it complex variables missing required field
+     */
     public function testComplexVariablesMissingRequiredField()
     {
         $this->expectFailsRule(new DefaultValuesOfCorrectType, '
@@ -77,10 +101,15 @@ class DefaultValuesOfCorrectTypeTest extends TestCase
         dog { name }
       }
         ', [
-            $this->badValue('a', 'ComplexInput', '{intField: 3}', 2, 53)
+            $this->badValue('a', 'ComplexInput', '{intField: 3}', 2, 53, [
+                'In field "requiredField": Expected "Boolean!", found null.'
+            ])
         ]);
     }
 
+    /**
+     * @it list variables with invalid item
+     */
     public function testListVariablesWithInvalidItem()
     {
         $this->expectFailsRule(new DefaultValuesOfCorrectType, '
@@ -88,22 +117,26 @@ class DefaultValuesOfCorrectTypeTest extends TestCase
         dog { name }
       }
         ', [
-            $this->badValue('a', '[String]', '["one", 2]', 2, 40)
+            $this->badValue('a', '[String]', '["one", 2]', 2, 40, [
+                'In element #1: Expected type "String", found 2.'
+            ])
         ]);
     }
 
     private function defaultForNonNullArg($varName, $typeName, $guessTypeName, $line, $column)
     {
         return FormattedError::create(
-            Messages::defaultForNonNullArgMessage($varName, $typeName, $guessTypeName),
+            DefaultValuesOfCorrectType::defaultForNonNullArgMessage($varName, $typeName, $guessTypeName),
             [ new SourceLocation($line, $column) ]
         );
     }
 
-    private function badValue($varName, $typeName, $val, $line, $column)
+    private function badValue($varName, $typeName, $val, $line, $column, $errors = null)
     {
+        $realErrors = !$errors ? ["Expected type \"$typeName\", found $val."] : $errors;
+
         return FormattedError::create(
-            Messages::badValueForDefaultArgMessage($varName, $typeName, $val),
+            DefaultValuesOfCorrectType::badValueForDefaultArgMessage($varName, $typeName, $val, $realErrors),
             [ new SourceLocation($line, $column) ]
         );
     }
diff --git a/tests/Validator/FieldsOnCorrectTypeTest.php b/tests/Validator/FieldsOnCorrectTypeTest.php
index ac5543a..09d4ce8 100644
--- a/tests/Validator/FieldsOnCorrectTypeTest.php
+++ b/tests/Validator/FieldsOnCorrectTypeTest.php
@@ -9,6 +9,10 @@ use GraphQL\Validator\Rules\FieldsOnCorrectType;
 class FieldsOnCorrectTypeTest extends TestCase
 {
     // Validate: Fields on correct type
+
+    /**
+     * @it Object field selection
+     */
     public function testObjectFieldSelection()
     {
         $this->expectPassesRule(new FieldsOnCorrectType(), '
@@ -19,6 +23,9 @@ class FieldsOnCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it Aliased object field selection
+     */
     public function testAliasedObjectFieldSelection()
     {
         $this->expectPassesRule(new FieldsOnCorrectType, '
@@ -29,6 +36,9 @@ class FieldsOnCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it Interface field selection
+     */
     public function testInterfaceFieldSelection()
     {
         $this->expectPassesRule(new FieldsOnCorrectType, '
@@ -39,6 +49,9 @@ class FieldsOnCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it Aliased interface field selection
+     */
     public function testAliasedInterfaceFieldSelection()
     {
         $this->expectPassesRule(new FieldsOnCorrectType, '
@@ -48,6 +61,9 @@ class FieldsOnCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it Lying alias selection
+     */
     public function testLyingAliasSelection()
     {
         $this->expectPassesRule(new FieldsOnCorrectType, '
@@ -57,6 +73,9 @@ class FieldsOnCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it Ignores fields on unknown type
+     */
     public function testIgnoresFieldsOnUnknownType()
     {
         $this->expectPassesRule(new FieldsOnCorrectType, '
@@ -66,17 +85,41 @@ class FieldsOnCorrectTypeTest extends TestCase
         ');
     }
 
+    /**
+     * @it reports errors when type is known again
+     */
+    public function testReportsErrorsWhenTypeIsKnownAgain()
+    {
+        $this->expectFailsRule(new FieldsOnCorrectType, '
+      fragment typeKnownAgain on Pet {
+        unknown_pet_field {
+          ... on Cat {
+            unknown_cat_field
+          }
+        }
+      }',
+            [ $this->undefinedField('unknown_pet_field', 'Pet', [], 3, 9),
+                $this->undefinedField('unknown_cat_field', 'Cat', [], 5, 13) ]
+        );
+    }
+
+    /**
+     * @it Field not defined on fragment
+     */
     public function testFieldNotDefinedOnFragment()
     {
         $this->expectFailsRule(new FieldsOnCorrectType, '
       fragment fieldNotDefined on Dog {
         meowVolume
       }',
-            [$this->undefinedField('meowVolume', 'Dog', 3, 9)]
+            [$this->undefinedField('meowVolume', 'Dog', [], 3, 9)]
         );
     }
 
-    public function testFieldNotDefinedDeeplyOnlyReportsFirst()
+    /**
+     * @it Ignores deeply unknown field
+     */
+    public function testIgnoresDeeplyUnknownField()
     {
         $this->expectFailsRule(new FieldsOnCorrectType, '
       fragment deepFieldNotDefined on Dog {
@@ -84,10 +127,13 @@ class FieldsOnCorrectTypeTest extends TestCase
           deeper_unknown_field
         }
       }',
-            [$this->undefinedField('unknown_field', 'Dog', 3, 9)]
+            [$this->undefinedField('unknown_field', 'Dog', [], 3, 9)]
         );
     }
 
+    /**
+     * @it Sub-field not defined
+     */
     public function testSubFieldNotDefined()
     {
         $this->expectFailsRule(new FieldsOnCorrectType, '
@@ -96,10 +142,13 @@ class FieldsOnCorrectTypeTest extends TestCase
           unknown_field
         }
       }',
-            [$this->undefinedField('unknown_field', 'Pet', 4, 11)]
+            [$this->undefinedField('unknown_field', 'Pet', [], 4, 11)]
         );
     }
 
+    /**
+     * @it Field not defined on inline fragment
+     */
     public function testFieldNotDefinedOnInlineFragment()
     {
         $this->expectFailsRule(new FieldsOnCorrectType, '
@@ -108,50 +157,65 @@ class FieldsOnCorrectTypeTest extends TestCase
           meowVolume
         }
       }',
-            [$this->undefinedField('meowVolume', 'Dog', 4, 11)]
+            [$this->undefinedField('meowVolume', 'Dog', [], 4, 11)]
         );
     }
 
+    /**
+     * @it Aliased field target not defined
+     */
     public function testAliasedFieldTargetNotDefined()
     {
         $this->expectFailsRule(new FieldsOnCorrectType, '
       fragment aliasedFieldTargetNotDefined on Dog {
         volume : mooVolume
       }',
-            [$this->undefinedField('mooVolume', 'Dog', 3, 9)]
+            [$this->undefinedField('mooVolume', 'Dog', [], 3, 9)]
         );
     }
 
+    /**
+     * @it Aliased lying field target not defined
+     */
     public function testAliasedLyingFieldTargetNotDefined()
     {
         $this->expectFailsRule(new FieldsOnCorrectType, '
       fragment aliasedLyingFieldTargetNotDefined on Dog {
         barkVolume : kawVolume
       }',
-            [$this->undefinedField('kawVolume', 'Dog', 3, 9)]
+            [$this->undefinedField('kawVolume', 'Dog', [], 3, 9)]
         );
     }
 
+    /**
+     * @it Not defined on interface
+     */
     public function testNotDefinedOnInterface()
     {
         $this->expectFailsRule(new FieldsOnCorrectType, '
       fragment notDefinedOnInterface on Pet {
         tailLength
       }',
-            [$this->undefinedField('tailLength', 'Pet', 3, 9)]
+            [$this->undefinedField('tailLength', 'Pet', [], 3, 9)]
         );
     }
 
+    /**
+     * @it Defined on implementors but not on interface
+     */
     public function testDefinedOnImplmentorsButNotOnInterface()
     {
         $this->expectFailsRule(new FieldsOnCorrectType, '
       fragment definedOnImplementorsButNotInterface on Pet {
         nickname
       }',
-            [$this->undefinedField('nickname', 'Pet', 3, 9)]
+            [$this->undefinedField('nickname', 'Pet', [ 'Cat', 'Dog' ], 3, 9)]
         );
     }
 
+    /**
+     * @it Meta field selection on union
+     */
     public function testMetaFieldSelectionOnUnion()
     {
         $this->expectPassesRule(new FieldsOnCorrectType, '
@@ -161,26 +225,35 @@ class FieldsOnCorrectTypeTest extends TestCase
         );
     }
 
+    /**
+     * @it Direct field selection on union
+     */
     public function testDirectFieldSelectionOnUnion()
     {
         $this->expectFailsRule(new FieldsOnCorrectType, '
       fragment directFieldSelectionOnUnion on CatOrDog {
         directField
       }',
-            [$this->undefinedField('directField', 'CatOrDog', 3, 9)]
+            [$this->undefinedField('directField', 'CatOrDog', [], 3, 9)]
         );
     }
 
+    /**
+     * @it Defined on implementors queried on union
+     */
     public function testDefinedOnImplementorsQueriedOnUnion()
     {
         $this->expectFailsRule(new FieldsOnCorrectType, '
       fragment definedOnImplementorsQueriedOnUnion on CatOrDog {
         name
       }',
-            [$this->undefinedField('name', 'CatOrDog', 3, 9)]
+            [$this->undefinedField('name', 'CatOrDog', [ 'Being', 'Pet', 'Canine', 'Cat', 'Dog' ], 3, 9)]
         );
     }
 
+    /**
+     * @it valid field in inline fragment
+     */
     public function testValidFieldInInlineFragment()
     {
         $this->expectPassesRule(new FieldsOnCorrectType, '
@@ -192,10 +265,45 @@ class FieldsOnCorrectTypeTest extends TestCase
         ');
     }
 
-    private function undefinedField($field, $type, $line, $column)
+    // Describe: Fields on correct type error message
+
+    /**
+     * @it Works with no suggestions
+     */
+    public function testWorksWithNoSuggestions()
+    {
+        $this->assertEquals('Cannot query field "T" on type "f".', FieldsOnCorrectType::undefinedFieldMessage('T', 'f', []));
+    }
+
+    /**
+     * @it Works with no small numbers of suggestions
+     */
+    public function testWorksWithNoSmallNumbersOfSuggestions()
+    {
+        $expected = 'Cannot query field "T" on type "f". ' .
+            'However, this field exists on "A", "B". ' .
+            'Perhaps you meant to use an inline fragment?';
+
+        $this->assertEquals($expected, FieldsOnCorrectType::undefinedFieldMessage('T', 'f', [ 'A', 'B' ]));
+    }
+
+    /**
+     * @it Works with lots of suggestions
+     */
+    public function testWorksWithLotsOfSuggestions()
+    {
+        $expected = 'Cannot query field "T" on type "f". ' .
+            'However, this field exists on "A", "B", "C", "D", "E", ' .
+            'and 1 other types. ' .
+            'Perhaps you meant to use an inline fragment?';
+
+        $this->assertEquals($expected, FieldsOnCorrectType::undefinedFieldMessage('T', 'f', [ 'A', 'B', 'C', 'D', 'E', 'F' ]));
+    }
+
+    private function undefinedField($field, $type, $suggestions, $line, $column)
     {
         return FormattedError::create(
-            Messages::undefinedFieldMessage($field, $type),
+            FieldsOnCorrectType::undefinedFieldMessage($field, $type, $suggestions),
             [new SourceLocation($line, $column)]
         );
     }
diff --git a/tests/Validator/FragmentsOnCompositeTypesTest.php b/tests/Validator/FragmentsOnCompositeTypesTest.php
index 4148bac..e1ad26e 100644
--- a/tests/Validator/FragmentsOnCompositeTypesTest.php
+++ b/tests/Validator/FragmentsOnCompositeTypesTest.php
@@ -9,6 +9,9 @@ class FragmentsOnCompositeTypesTest extends TestCase
 {
     // Validate: Fragments on composite types
 
+    /**
+     * @it object is valid fragment type
+     */
     public function testObjectIsValidFragmentType()
     {
         $this->expectPassesRule(new FragmentsOnCompositeTypes, '
@@ -18,6 +21,9 @@ class FragmentsOnCompositeTypesTest extends TestCase
         ');
     }
 
+    /**
+     * @it interface is valid fragment type
+     */
     public function testInterfaceIsValidFragmentType()
     {
         $this->expectPassesRule(new FragmentsOnCompositeTypes, '
@@ -27,6 +33,9 @@ class FragmentsOnCompositeTypesTest extends TestCase
         ');
     }
 
+    /**
+     * @it object is valid inline fragment type
+     */
     public function testObjectIsValidInlineFragmentType()
     {
         $this->expectPassesRule(new FragmentsOnCompositeTypes, '
@@ -38,6 +47,23 @@ class FragmentsOnCompositeTypesTest extends TestCase
         ');
     }
 
+    /**
+     * @it inline fragment without type is valid
+     */
+    public function testInlineFragmentWithoutTypeIsValid()
+    {
+        $this->expectPassesRule(new FragmentsOnCompositeTypes, '
+      fragment validFragment on Pet {
+        ... {
+          name
+        }
+      }
+        ');
+    }
+
+    /**
+     * @it union is valid fragment type
+     */
     public function testUnionIsValidFragmentType()
     {
         $this->expectPassesRule(new FragmentsOnCompositeTypes, '
@@ -47,6 +73,9 @@ class FragmentsOnCompositeTypesTest extends TestCase
         ');
     }
 
+    /**
+     * @it scalar is invalid fragment type
+     */
     public function testScalarIsInvalidFragmentType()
     {
         $this->expectFailsRule(new FragmentsOnCompositeTypes, '
@@ -57,6 +86,9 @@ class FragmentsOnCompositeTypesTest extends TestCase
             [$this->error('scalarFragment', 'Boolean', 2, 34)]);
     }
 
+    /**
+     * @it enum is invalid fragment type
+     */
     public function testEnumIsInvalidFragmentType()
     {
         $this->expectFailsRule(new FragmentsOnCompositeTypes, '
@@ -67,6 +99,9 @@ class FragmentsOnCompositeTypesTest extends TestCase
             [$this->error('scalarFragment', 'FurColor', 2, 34)]);
     }
 
+    /**
+     * @it input object is invalid fragment type
+     */
     public function testInputObjectIsInvalidFragmentType()
     {
         $this->expectFailsRule(new FragmentsOnCompositeTypes, '
@@ -77,6 +112,9 @@ class FragmentsOnCompositeTypesTest extends TestCase
             [$this->error('inputFragment', 'ComplexInput', 2, 33)]);
     }
 
+    /**
+     * @it scalar is invalid inline fragment type
+     */
     public function testScalarIsInvalidInlineFragmentType()
     {
         $this->expectFailsRule(new FragmentsOnCompositeTypes, '
diff --git a/tests/Validator/KnownArgumentNamesTest.php b/tests/Validator/KnownArgumentNamesTest.php
index dba1e2f..dece1a8 100644
--- a/tests/Validator/KnownArgumentNamesTest.php
+++ b/tests/Validator/KnownArgumentNamesTest.php
@@ -8,6 +8,10 @@ use GraphQL\Validator\Rules\KnownArgumentNames;
 class KnownArgumentNamesTest extends TestCase
 {
     // Validate: Known argument names:
+
+    /**
+     * @it single arg is known
+     */
     public function testSingleArgIsKnown()
     {
         $this->expectPassesRule(new KnownArgumentNames, '
@@ -17,6 +21,9 @@ class KnownArgumentNamesTest extends TestCase
         ');
     }
 
+    /**
+     * @it multiple args are known
+     */
     public function testMultipleArgsAreKnown()
     {
         $this->expectPassesRule(new KnownArgumentNames, '
@@ -26,6 +33,9 @@ class KnownArgumentNamesTest extends TestCase
         ');
     }
 
+    /**
+     * @it ignores args of unknown fields
+     */
     public function testIgnoresArgsOfUnknownFields()
     {
         $this->expectPassesRule(new KnownArgumentNames, '
@@ -35,6 +45,9 @@ class KnownArgumentNamesTest extends TestCase
         ');
     }
 
+    /**
+     * @it multiple args in reverse order are known
+     */
     public function testMultipleArgsInReverseOrderAreKnown()
     {
         $this->expectPassesRule(new KnownArgumentNames, '
@@ -44,6 +57,9 @@ class KnownArgumentNamesTest extends TestCase
         ');
     }
 
+    /**
+     * @it no args on optional arg
+     */
     public function testNoArgsOnOptionalArg()
     {
         $this->expectPassesRule(new KnownArgumentNames, '
@@ -53,6 +69,9 @@ class KnownArgumentNamesTest extends TestCase
         ');
     }
 
+    /**
+     * @it args are known deeply
+     */
     public function testArgsAreKnownDeeply()
     {
         $this->expectPassesRule(new KnownArgumentNames, '
@@ -71,6 +90,9 @@ class KnownArgumentNamesTest extends TestCase
         ');
     }
 
+    /**
+     * @it directive args are known
+     */
     public function testDirectiveArgsAreKnown()
     {
         $this->expectPassesRule(new KnownArgumentNames, '
@@ -80,6 +102,9 @@ class KnownArgumentNamesTest extends TestCase
         ');
     }
 
+    /**
+     * @it undirective args are invalid
+     */
     public function testUndirectiveArgsAreInvalid()
     {
         $this->expectFailsRule(new KnownArgumentNames, '
@@ -91,6 +116,9 @@ class KnownArgumentNamesTest extends TestCase
         ]);
     }
 
+    /**
+     * @it invalid arg name
+     */
     public function testInvalidArgName()
     {
         $this->expectFailsRule(new KnownArgumentNames, '
@@ -102,6 +130,9 @@ class KnownArgumentNamesTest extends TestCase
         ]);
     }
 
+    /**
+     * @it unknown args amongst known args
+     */
     public function testUnknownArgsAmongstKnownArgs()
     {
         $this->expectFailsRule(new KnownArgumentNames, '
@@ -114,6 +145,9 @@ class KnownArgumentNamesTest extends TestCase
         ]);
     }
 
+    /**
+     * @it unknown args deeply
+     */
     public function testUnknownArgsDeeply()
     {
         $this->expectFailsRule(new KnownArgumentNames, '
diff --git a/tests/Validator/KnownDirectivesTest.php b/tests/Validator/KnownDirectivesTest.php
index 50ec3e4..990ab30 100644
--- a/tests/Validator/KnownDirectivesTest.php
+++ b/tests/Validator/KnownDirectivesTest.php
@@ -8,6 +8,10 @@ use GraphQL\Validator\Rules\KnownDirectives;
 class KnownDirectivesTest extends TestCase
 {
     // Validate: Known directives
+
+    /**
+     * @it with no directives
+     */
     public function testWithNoDirectives()
     {
         $this->expectPassesRule(new KnownDirectives, '
@@ -22,6 +26,9 @@ class KnownDirectivesTest extends TestCase
         ');
     }
 
+    /**
+     * @it with known directives
+     */
     public function testWithKnownDirectives()
     {
         $this->expectPassesRule(new KnownDirectives, '
@@ -36,6 +43,9 @@ class KnownDirectivesTest extends TestCase
         ');
     }
 
+    /**
+     * @it with unknown directive
+     */
     public function testWithUnknownDirective()
     {
         $this->expectFailsRule(new KnownDirectives, '
@@ -49,6 +59,9 @@ class KnownDirectivesTest extends TestCase
         ]);
     }
 
+    /**
+     * @it with many unknown directives
+     */
     public function testWithManyUnknownDirectives()
     {
         $this->expectFailsRule(new KnownDirectives, '
@@ -70,6 +83,9 @@ class KnownDirectivesTest extends TestCase
         ]);
     }
 
+    /**
+     * @it with well placed directives
+     */
     public function testWithWellPlacedDirectives()
     {
         $this->expectPassesRule(new KnownDirectives, '
@@ -82,15 +98,20 @@ class KnownDirectivesTest extends TestCase
         ');
     }
 
+    /**
+     * @it with misplaced directives
+     */
     public function testWithMisplacedDirectives()
     {
         $this->expectFailsRule(new KnownDirectives, '
       query Foo @include(if: true) {
-        name
-        ...Frag
+        name @operationOnly
+        ...Frag @operationOnly
       }
         ', [
-            $this->misplacedDirective('include', 'operation', 2, 17)
+            $this->misplacedDirective('include', 'QUERY', 2, 17),
+            $this->misplacedDirective('operationOnly', 'FIELD', 3, 14),
+            $this->misplacedDirective('operationOnly', 'FRAGMENT_SPREAD', 4, 17),
         ]);
     }
 
diff --git a/tests/Validator/KnownFragmentNamesTest.php b/tests/Validator/KnownFragmentNamesTest.php
index 1a39ff1..36ba408 100644
--- a/tests/Validator/KnownFragmentNamesTest.php
+++ b/tests/Validator/KnownFragmentNamesTest.php
@@ -9,6 +9,9 @@ class KnownFragmentNamesTest extends TestCase
 {
     // Validate: Known fragment names
 
+    /**
+     * @it known fragment names are valid
+     */
     public function testKnownFragmentNamesAreValid()
     {
         $this->expectPassesRule(new KnownFragmentNames, '
@@ -33,6 +36,9 @@ class KnownFragmentNamesTest extends TestCase
         ');
     }
 
+    /**
+     * @it unknown fragment names are invalid
+     */
     public function testUnknownFragmentNamesAreInvalid()
     {
         $this->expectFailsRule(new KnownFragmentNames, '
diff --git a/tests/Validator/KnownTypeNamesTest.php b/tests/Validator/KnownTypeNamesTest.php
index b9994ef..467b9dc 100644
--- a/tests/Validator/KnownTypeNamesTest.php
+++ b/tests/Validator/KnownTypeNamesTest.php
@@ -9,6 +9,9 @@ class KnownTypeNamesTest extends TestCase
 {
     // Validate: Known type names
 
+    /**
+     * @it known type names are valid
+     */
     public function testKnownTypeNamesAreValid()
     {
         $this->expectPassesRule(new KnownTypeNames, '
@@ -23,6 +26,9 @@ class KnownTypeNamesTest extends TestCase
         ');
     }
 
+    /**
+     * @it unknown type names are invalid
+     */
     public function testUnknownTypeNamesAreInvalid()
     {
         $this->expectFailsRule(new KnownTypeNames, '
@@ -42,6 +48,32 @@ class KnownTypeNamesTest extends TestCase
         ]);
     }
 
+    /**
+     * @it ignores type definitions
+     */
+    public function testIgnoresTypeDefinitions()
+    {
+        $this->expectFailsRule(new KnownTypeNames, '
+      type NotInTheSchema {
+        field: FooBar
+      }
+      interface FooBar {
+        field: NotInTheSchema
+      }
+      union U = A | B
+      input Blob {
+        field: UnknownType
+      }
+      query Foo($var: NotInTheSchema) {
+        user(id: $var) {
+          id
+        }
+      }
+    ', [
+            $this->unknownType('NotInTheSchema', 12, 23),
+        ]);
+    }
+
     private function unknownType($typeName, $line, $column)
     {
         return FormattedError::create(
diff --git a/tests/Validator/LoneAnonymousOperationTest.php b/tests/Validator/LoneAnonymousOperationTest.php
new file mode 100644
index 0000000..d0d5e72
--- /dev/null
+++ b/tests/Validator/LoneAnonymousOperationTest.php
@@ -0,0 +1,127 @@
+<?php
+namespace GraphQL\Tests\Validator;
+
+use GraphQL\FormattedError;
+use GraphQL\Language\SourceLocation;
+use GraphQL\Validator\Rules\LoneAnonymousOperation;
+
+class LoneAnonymousOperationTest extends TestCase
+{
+    // Validate: Anonymous operation must be alone
+
+    /**
+     * @it no operations
+     */
+    public function testNoOperations()
+    {
+        $this->expectPassesRule(new LoneAnonymousOperation, '
+      fragment fragA on Type {
+        field
+      }
+        ');
+    }
+
+    /**
+     * @it one anon operation
+     */
+    public function testOneAnonOperation()
+    {
+        $this->expectPassesRule(new LoneAnonymousOperation, '
+      {
+        field
+      }
+        ');
+    }
+
+    /**
+     * @it multiple named operations
+     */
+    public function testMultipleNamedOperations()
+    {
+        $this->expectPassesRule(new LoneAnonymousOperation, '
+      query Foo {
+        field
+      }
+
+      query Bar {
+        field
+      }
+        ');
+    }
+
+    /**
+     * @it anon operation with fragment
+     */
+    public function testAnonOperationWithFragment()
+    {
+        $this->expectPassesRule(new LoneAnonymousOperation, '
+      {
+        ...Foo
+      }
+      fragment Foo on Type {
+        field
+      }
+        ');
+    }
+
+    /**
+     * @it multiple anon operations
+     */
+    public function testMultipleAnonOperations()
+    {
+        $this->expectFailsRule(new LoneAnonymousOperation, '
+      {
+        fieldA
+      }
+      {
+        fieldB
+      }
+        ', [
+            $this->anonNotAlone(2, 7),
+            $this->anonNotAlone(5, 7)
+        ]);
+    }
+
+    /**
+     * @it anon operation with a mutation
+     */
+    public function testAnonOperationWithMutation()
+    {
+        $this->expectFailsRule(new LoneAnonymousOperation, '
+      {
+        fieldA
+      }
+      mutation Foo {
+        fieldB
+      }
+        ', [
+            $this->anonNotAlone(2, 7)
+        ]);
+    }
+
+    /**
+     * @it anon operation with a subscription
+     */
+    public function testAnonOperationWithSubscription()
+    {
+        $this->expectFailsRule(new LoneAnonymousOperation, '
+      {
+        fieldA
+      }
+      subscription Foo {
+        fieldB
+      }
+        ', [
+            $this->anonNotAlone(2, 7)
+        ]);
+    }
+
+    private function anonNotAlone($line, $column)
+    {
+        return FormattedError::create(
+            LoneAnonymousOperation::anonOperationNotAloneMessage(),
+            [new SourceLocation($line, $column)]
+        );
+
+    }
+}
\ No newline at end of file
diff --git a/tests/Validator/NoFragmentCyclesTest.php b/tests/Validator/NoFragmentCyclesTest.php
index 8704bb3..cfb9aa5 100644
--- a/tests/Validator/NoFragmentCyclesTest.php
+++ b/tests/Validator/NoFragmentCyclesTest.php
@@ -9,6 +9,9 @@ class NoFragmentCyclesTest extends TestCase
 {
     // Validate: No circular fragment spreads
 
+    /**
+     * @it single reference is valid
+     */
     public function testSingleReferenceIsValid()
     {
         $this->expectPassesRule(new NoFragmentCycles(), '
@@ -17,6 +20,9 @@ class NoFragmentCyclesTest extends TestCase
         ');
     }
 
+    /**
+     * @it spreading twice is not circular
+     */
     public function testSpreadingTwiceIsNotCircular()
     {
         $this->expectPassesRule(new NoFragmentCycles, '
@@ -25,6 +31,9 @@ class NoFragmentCyclesTest extends TestCase
         ');
     }
 
+    /**
+     * @it spreading twice indirectly is not circular
+     */
     public function testSpreadingTwiceIndirectlyIsNotCircular()
     {
         $this->expectPassesRule(new NoFragmentCycles, '
@@ -34,6 +43,9 @@ class NoFragmentCyclesTest extends TestCase
         ');
     }
 
+    /**
+     * @it double spread within abstract types
+     */
     public function testDoubleSpreadWithinAbstractTypes()
     {
         $this->expectPassesRule(new NoFragmentCycles, '
@@ -49,6 +61,21 @@ class NoFragmentCyclesTest extends TestCase
         ');
     }
 
+    /**
+     * @it does not false positive on unknown fragment
+     */
+    public function testDoesNotFalsePositiveOnUnknownFragment()
+    {
+        $this->expectPassesRule(new NoFragmentCycles, '
+      fragment nameFragment on Pet {
+        ...UnknownFragment
+      }
+        ');
+    }
+
+    /**
+     * @it spreading recursively within field fails
+     */
     public function testSpreadingRecursivelyWithinFieldFails()
     {
         $this->expectFailsRule(new NoFragmentCycles, '
@@ -58,6 +85,9 @@ class NoFragmentCyclesTest extends TestCase
         ]);
     }
 
+    /**
+     * @it no spreading itself directly
+     */
     public function testNoSpreadingItselfDirectly()
     {
         $this->expectFailsRule(new NoFragmentCycles, '
@@ -67,6 +97,9 @@ class NoFragmentCyclesTest extends TestCase
         ]);
     }
 
+    /**
+     * @it no spreading itself directly within inline fragment
+     */
     public function testNoSpreadingItselfDirectlyWithinInlineFragment()
     {
         $this->expectFailsRule(new NoFragmentCycles, '
@@ -80,6 +113,9 @@ class NoFragmentCyclesTest extends TestCase
         ]);
     }
 
+    /**
+     * @it no spreading itself indirectly
+     */
     public function testNoSpreadingItselfIndirectly()
     {
         $this->expectFailsRule(new NoFragmentCycles, '
@@ -93,6 +129,9 @@ class NoFragmentCyclesTest extends TestCase
         ]);
     }
 
+    /**
+     * @it no spreading itself indirectly reports opposite order
+     */
     public function testNoSpreadingItselfIndirectlyReportsOppositeOrder()
     {
         $this->expectFailsRule(new NoFragmentCycles, '
@@ -106,6 +145,9 @@ class NoFragmentCyclesTest extends TestCase
         ]);
     }
 
+    /**
+     * @it no spreading itself indirectly within inline fragment
+     */
     public function testNoSpreadingItselfIndirectlyWithinInlineFragment()
     {
         $this->expectFailsRule(new NoFragmentCycles, '
@@ -127,6 +169,9 @@ class NoFragmentCyclesTest extends TestCase
         ]);
     }
 
+    /**
+     * @it no spreading itself deeply
+     */
     public function testNoSpreadingItselfDeeply()
     {
         $this->expectFailsRule(new NoFragmentCycles, '
@@ -136,30 +181,36 @@ class NoFragmentCyclesTest extends TestCase
       fragment fragX on Dog { ...fragY }
       fragment fragY on Dog { ...fragZ }
       fragment fragZ on Dog { ...fragO }
-      fragment fragO on Dog { ...fragA, ...fragX }
+      fragment fragO on Dog { ...fragP }
+      fragment fragP on Dog { ...fragA, ...fragX }
     ', [
             FormattedError::create(
-                NoFragmentCycles::cycleErrorMessage('fragA', ['fragB', 'fragC', 'fragO']),
+                NoFragmentCycles::cycleErrorMessage('fragA', [ 'fragB', 'fragC', 'fragO', 'fragP' ]),
                 [
                     new SourceLocation(2, 31),
                     new SourceLocation(3, 31),
                     new SourceLocation(4, 31),
                     new SourceLocation(8, 31),
+                    new SourceLocation(9, 31),
                 ]
             ),
             FormattedError::create(
-                NoFragmentCycles::cycleErrorMessage('fragX', ['fragY', 'fragZ', 'fragO']),
+                NoFragmentCycles::cycleErrorMessage('fragO', [ 'fragP', 'fragX', 'fragY', 'fragZ' ]),
                 [
+                    new SourceLocation(8, 31),
+                    new SourceLocation(9, 41),
                     new SourceLocation(5, 31),
                     new SourceLocation(6, 31),
                     new SourceLocation(7, 31),
-                    new SourceLocation(8, 41),
                 ]
             )
         ]);
     }
 
-    public function testNoSpreadingItselfDeeplyTwoPathsNewRule()
+    /**
+     * @it no spreading itself deeply two paths
+     */
+    public function testNoSpreadingItselfDeeplyTwoPaths()
     {
         $this->expectFailsRule(new NoFragmentCycles, '
       fragment fragA on Dog { ...fragB, ...fragC }
@@ -177,6 +228,56 @@ class NoFragmentCyclesTest extends TestCase
         ]);
     }
 
+    /**
+     * @it no spreading itself deeply two paths -- alt traverse order
+     */
+    public function testNoSpreadingItselfDeeplyTwoPathsTraverseOrder()
+    {
+        $this->expectFailsRule(new NoFragmentCycles, '
+      fragment fragA on Dog { ...fragC }
+      fragment fragB on Dog { ...fragC }
+      fragment fragC on Dog { ...fragA, ...fragB }
+    ', [
+            FormattedError::create(
+                NoFragmentCycles::cycleErrorMessage('fragA', [ 'fragC' ]),
+                [new SourceLocation(2,31), new SourceLocation(4,31)]
+            ),
+            FormattedError::create(
+                NoFragmentCycles::cycleErrorMessage('fragC', [ 'fragB' ]),
+                [new SourceLocation(4, 41), new SourceLocation(3, 31)]
+            )
+        ]);
+    }
+
+    /**
+     * @it no spreading itself deeply and immediately
+     */
+    public function testNoSpreadingItselfDeeplyAndImmediately()
+    {
+        $this->expectFailsRule(new NoFragmentCycles, '
+      fragment fragA on Dog { ...fragB }
+      fragment fragB on Dog { ...fragB, ...fragC }
+      fragment fragC on Dog { ...fragA, ...fragB }
+    ', [
+            FormattedError::create(
+                NoFragmentCycles::cycleErrorMessage('fragB', []),
+                [new SourceLocation(3, 31)]
+            ),
+            FormattedError::create(
+                NoFragmentCycles::cycleErrorMessage('fragA', [ 'fragB', 'fragC' ]),
+                [
+                    new SourceLocation(2, 31),
+                    new SourceLocation(3, 41),
+                    new SourceLocation(4, 31)
+                ]
+            ),
+            FormattedError::create(
+                NoFragmentCycles::cycleErrorMessage('fragB', [ 'fragC' ]),
+                [new SourceLocation(3, 41), new SourceLocation(4, 41)]
+            )
+        ]);
+    }
+
     private function cycleError($fargment, $spreadNames, $line, $column)
     {
         return FormattedError::create(
diff --git a/tests/Validator/NoUndefinedVariablesTest.php b/tests/Validator/NoUndefinedVariablesTest.php
index a91b70e..6bc86a3 100644
--- a/tests/Validator/NoUndefinedVariablesTest.php
+++ b/tests/Validator/NoUndefinedVariablesTest.php
@@ -9,6 +9,9 @@ class NoUndefinedVariablesTest extends TestCase
 {
     // Validate: No undefined variables
 
+    /**
+     * @it all variables defined
+     */
     public function testAllVariablesDefined()
     {
         $this->expectPassesRule(new NoUndefinedVariables(), '
@@ -18,6 +21,9 @@ class NoUndefinedVariablesTest extends TestCase
         ');
     }
 
+    /**
+     * @it all variables deeply defined
+     */
     public function testAllVariablesDeeplyDefined()
     {
         $this->expectPassesRule(new NoUndefinedVariables, '
@@ -31,6 +37,9 @@ class NoUndefinedVariablesTest extends TestCase
         ');
     }
 
+    /**
+     * @it all variables deeply in inline fragments defined
+     */
     public function testAllVariablesDeeplyInInlineFragmentsDefined()
     {
         $this->expectPassesRule(new NoUndefinedVariables, '
@@ -48,6 +57,9 @@ class NoUndefinedVariablesTest extends TestCase
         ');
     }
 
+    /**
+     * @it all variables in fragments deeply defined
+     */
     public function testAllVariablesInFragmentsDeeplyDefined()
     {
         $this->expectPassesRule(new NoUndefinedVariables, '
@@ -70,6 +82,9 @@ class NoUndefinedVariablesTest extends TestCase
         ');
     }
 
+    /**
+     * @it variable within single fragment defined in multiple operations
+     */
     public function testVariableWithinSingleFragmentDefinedInMultipleOperations()
     {
         // variable within single fragment defined in multiple operations
@@ -86,6 +101,9 @@ class NoUndefinedVariablesTest extends TestCase
         ');
     }
 
+    /**
+     * @it variable within fragments defined in operations
+     */
     public function testVariableWithinFragmentsDefinedInOperations()
     {
         $this->expectPassesRule(new NoUndefinedVariables, '
@@ -104,6 +122,9 @@ class NoUndefinedVariablesTest extends TestCase
         ');
     }
 
+    /**
+     * @it variable within recursive fragment defined
+     */
     public function testVariableWithinRecursiveFragmentDefined()
     {
         $this->expectPassesRule(new NoUndefinedVariables, '
@@ -118,6 +139,9 @@ class NoUndefinedVariablesTest extends TestCase
         ');
     }
 
+    /**
+     * @it variable not defined
+     */
     public function testVariableNotDefined()
     {
         $this->expectFailsRule(new NoUndefinedVariables, '
@@ -125,10 +149,13 @@ class NoUndefinedVariablesTest extends TestCase
         field(a: $a, b: $b, c: $c, d: $d)
       }
         ', [
-            $this->undefVar('d', 3, 39)
+            $this->undefVar('d', 3, 39, 'Foo', 2, 7)
         ]);
     }
 
+    /**
+     * @it variable not defined by un-named query
+     */
     public function testVariableNotDefinedByUnNamedQuery()
     {
         $this->expectFailsRule(new NoUndefinedVariables, '
@@ -136,10 +163,13 @@ class NoUndefinedVariablesTest extends TestCase
         field(a: $a)
       }
         ', [
-            $this->undefVar('a', 3, 18)
+            $this->undefVar('a', 3, 18, '', 2, 7)
         ]);
     }
 
+    /**
+     * @it multiple variables not defined
+     */
     public function testMultipleVariablesNotDefined()
     {
         $this->expectFailsRule(new NoUndefinedVariables, '
@@ -147,11 +177,14 @@ class NoUndefinedVariablesTest extends TestCase
         field(a: $a, b: $b, c: $c)
       }
         ', [
-            $this->undefVar('a', 3, 18),
-            $this->undefVar('c', 3, 32)
+            $this->undefVar('a', 3, 18, 'Foo', 2, 7),
+            $this->undefVar('c', 3, 32, 'Foo', 2, 7)
         ]);
     }
 
+    /**
+     * @it variable in fragment not defined by un-named query
+     */
     public function testVariableInFragmentNotDefinedByUnNamedQuery()
     {
         $this->expectFailsRule(new NoUndefinedVariables, '
@@ -162,10 +195,13 @@ class NoUndefinedVariablesTest extends TestCase
         field(a: $a)
       }
         ', [
-            $this->undefVar('a', 6, 18)
+            $this->undefVar('a', 6, 18, '', 2, 7)
         ]);
     }
 
+    /**
+     * @it variable in fragment not defined by operation
+     */
     public function testVariableInFragmentNotDefinedByOperation()
     {
         $this->expectFailsRule(new NoUndefinedVariables, '
@@ -186,10 +222,13 @@ class NoUndefinedVariablesTest extends TestCase
         field(c: $c)
       }
         ', [
-            $this->undefVarByOp('c', 16, 18, 'Foo', 2, 7)
+            $this->undefVar('c', 16, 18, 'Foo', 2, 7)
         ]);
     }
 
+    /**
+     * @it multiple variables in fragments not defined
+     */
     public function testMultipleVariablesInFragmentsNotDefined()
     {
         $this->expectFailsRule(new NoUndefinedVariables, '
@@ -210,11 +249,14 @@ class NoUndefinedVariablesTest extends TestCase
         field(c: $c)
       }
         ', [
-            $this->undefVarByOp('a', 6, 18, 'Foo', 2, 7),
-            $this->undefVarByOp('c', 16, 18, 'Foo', 2, 7)
+            $this->undefVar('a', 6, 18, 'Foo', 2, 7),
+            $this->undefVar('c', 16, 18, 'Foo', 2, 7)
         ]);
     }
 
+    /**
+     * @it single variable in fragment not defined by multiple operations
+     */
     public function testSingleVariableInFragmentNotDefinedByMultipleOperations()
     {
         $this->expectFailsRule(new NoUndefinedVariables, '
@@ -228,11 +270,14 @@ class NoUndefinedVariablesTest extends TestCase
         field(a: $a, b: $b)
       }
         ', [
-            $this->undefVarByOp('b', 9, 25, 'Foo', 2, 7),
-            $this->undefVarByOp('b', 9, 25, 'Bar', 5, 7)
+            $this->undefVar('b', 9, 25, 'Foo', 2, 7),
+            $this->undefVar('b', 9, 25, 'Bar', 5, 7)
         ]);
     }
 
+    /**
+     * @it variables in fragment not defined by multiple operations
+     */
     public function testVariablesInFragmentNotDefinedByMultipleOperations()
     {
         $this->expectFailsRule(new NoUndefinedVariables, '
@@ -246,11 +291,14 @@ class NoUndefinedVariablesTest extends TestCase
         field(a: $a, b: $b)
       }
         ', [
-            $this->undefVarByOp('a', 9, 18, 'Foo', 2, 7),
-            $this->undefVarByOp('b', 9, 25, 'Bar', 5, 7)
+            $this->undefVar('a', 9, 18, 'Foo', 2, 7),
+            $this->undefVar('b', 9, 25, 'Bar', 5, 7)
         ]);
     }
 
+    /**
+     * @it variable in fragment used by other operation
+     */
     public function testVariableInFragmentUsedByOtherOperation()
     {
         $this->expectFailsRule(new NoUndefinedVariables, '
@@ -267,11 +315,14 @@ class NoUndefinedVariablesTest extends TestCase
         field(b: $b)
       }
         ', [
-            $this->undefVarByOp('a', 9, 18, 'Foo', 2, 7),
-            $this->undefVarByOp('b', 12, 18, 'Bar', 5, 7)
+            $this->undefVar('a', 9, 18, 'Foo', 2, 7),
+            $this->undefVar('b', 12, 18, 'Bar', 5, 7)
         ]);
     }
 
+    /**
+     * @it multiple undefined variables produce multiple errors
+     */
     public function testMultipleUndefinedVariablesProduceMultipleErrors()
     {
         $this->expectFailsRule(new NoUndefinedVariables, '
@@ -290,29 +341,27 @@ class NoUndefinedVariablesTest extends TestCase
         field2(c: $c)
       }
     ', [
-            $this->undefVarByOp('a', 9, 19, 'Foo', 2, 7),
-            $this->undefVarByOp('c', 14, 19, 'Foo', 2, 7),
-            $this->undefVarByOp('a', 11, 19, 'Foo', 2, 7),
-            $this->undefVarByOp('b', 9, 26, 'Bar', 5, 7),
-            $this->undefVarByOp('c', 14, 19, 'Bar', 5, 7),
-            $this->undefVarByOp('b', 11, 26, 'Bar', 5, 7),
+            $this->undefVar('a', 9, 19, 'Foo', 2, 7),
+            $this->undefVar('a', 11, 19, 'Foo', 2, 7),
+            $this->undefVar('c', 14, 19, 'Foo', 2, 7),
+            $this->undefVar('b', 9, 26, 'Bar', 5, 7),
+            $this->undefVar('b', 11, 26, 'Bar', 5, 7),
+            $this->undefVar('c', 14, 19, 'Bar', 5, 7),
         ]);
     }
 
 
-    private function undefVar($varName, $line, $column)
+    private function undefVar($varName, $line, $column, $opName = null, $l2 = null, $c2 = null)
     {
-        return FormattedError::create(
-            NoUndefinedVariables::undefinedVarMessage($varName),
-            [new SourceLocation($line, $column)]
-        );
-    }
+        $locs = [new SourceLocation($line, $column)];
+
+        if ($l2 && $c2) {
+            $locs[] = new SourceLocation($l2, $c2);
+        }
 
-    private function undefVarByOp($varName, $l1, $c1, $opName, $l2, $c2)
-    {
         return FormattedError::create(
-            NoUndefinedVariables::undefinedVarByOpMessage($varName, $opName),
-            [new SourceLocation($l1, $c1), new SourceLocation($l2, $c2)]
+            NoUndefinedVariables::undefinedVarMessage($varName, $opName),
+            $locs
         );
     }
 }
diff --git a/tests/Validator/NoUnusedFragmentsTest.php b/tests/Validator/NoUnusedFragmentsTest.php
index 15b2152..53d5373 100644
--- a/tests/Validator/NoUnusedFragmentsTest.php
+++ b/tests/Validator/NoUnusedFragmentsTest.php
@@ -8,6 +8,10 @@ use GraphQL\Validator\Rules\NoUnusedFragments;
 class NoUnusedFragmentsTest extends TestCase
 {
     // Validate: No unused fragments
+
+    /**
+     * @it all fragment names are used
+     */
     public function testAllFragmentNamesAreUsed()
     {
         $this->expectPassesRule(new NoUnusedFragments(), '
@@ -32,6 +36,9 @@ class NoUnusedFragmentsTest extends TestCase
         ');
     }
 
+    /**
+     * @it all fragment names are used by multiple operations
+     */
     public function testAllFragmentNamesAreUsedByMultipleOperations()
     {
         $this->expectPassesRule(new NoUnusedFragments, '
@@ -58,6 +65,9 @@ class NoUnusedFragmentsTest extends TestCase
         ');
     }
 
+    /**
+     * @it contains unknown fragments
+     */
     public function testContainsUnknownFragments()
     {
         $this->expectFailsRule(new NoUnusedFragments, '
@@ -93,6 +103,9 @@ class NoUnusedFragmentsTest extends TestCase
         ]);
     }
 
+    /**
+     * @it contains unknown fragments with ref cycle
+     */
     public function testContainsUnknownFragmentsWithRefCycle()
     {
         $this->expectFailsRule(new NoUnusedFragments, '
@@ -130,6 +143,9 @@ class NoUnusedFragmentsTest extends TestCase
         ]);
     }
 
+    /**
+     * @it contains unknown and undef fragments
+     */
     public function testContainsUnknownAndUndefFragments()
     {
 
diff --git a/tests/Validator/TestCase.php b/tests/Validator/TestCase.php
index c2a6ed9..0df6386 100644
--- a/tests/Validator/TestCase.php
+++ b/tests/Validator/TestCase.php
@@ -3,6 +3,7 @@ namespace GraphQL\Tests\Validator;
 
 use GraphQL\Language\Parser;
 use GraphQL\Schema;
+use GraphQL\Type\Definition\Directive;
 use GraphQL\Type\Definition\EnumType;
 use GraphQL\Type\Definition\InputObjectType;
 use GraphQL\Type\Definition\InterfaceType;
@@ -43,12 +44,24 @@ abstract class TestCase extends \PHPUnit_Framework_TestCase
             ],
         ]);
 
+        $Canine = new InterfaceType([
+            'name' => 'Canine',
+            'fields' => function() {
+                return [
+                    'name' => [
+                        'type' => Type::string(),
+                        'args' => ['surname' => ['type' => Type::boolean()]]
+                    ]
+                ];
+            }
+        ]);
+
         $DogCommand = new EnumType([
             'name' => 'DogCommand',
             'values' => [
                 'SIT' => ['value' => 0],
                 'HEEL' => ['value' => 1],
-                'DOWN' => ['value' => 3]
+                'DOWN' => ['value' => 2]
             ]
         ]);
 
@@ -76,7 +89,7 @@ abstract class TestCase extends \PHPUnit_Framework_TestCase
                     'args' => ['x' => ['type' => Type::int()], 'y' => ['type' => Type::int()]]
                 ]
             ],
-            'interfaces' => [$Being, $Pet]
+            'interfaces' => [$Being, $Pet, $Canine]
         ]);
 
         $Cat = new ObjectType([
@@ -277,7 +290,15 @@ abstract class TestCase extends \PHPUnit_Framework_TestCase
             ]
         ]);
 
-        $defaultSchema = new Schema($queryRoot);
+        $defaultSchema = new Schema([
+            'query' => $queryRoot,
+            'directives' => [
+                new Directive([
+                    'name' => 'operationOnly',
+                    'locations' => [ 'QUERY' ],
+                ])
+            ]
+        ]);
         return $defaultSchema;
     }