diff --git a/src/Type/Definition/Config.php b/src/Type/Definition/Config.php
index bffef16..5eaa68a 100644
--- a/src/Type/Definition/Config.php
+++ b/src/Type/Definition/Config.php
@@ -59,6 +59,14 @@ class Config
         self::$allowCustomOptions = $allowCustomOptions;
     }
 
+    /**
+     * @return bool
+     */
+    public static function isValidationEnabled()
+    {
+        return self::$enableValidation;
+    }
+
     /**
      * @param array $config
      * @param array $definition
@@ -90,20 +98,6 @@ class Config
         }
     }
 
-    /**
-     * @param $definition
-     * @param int $flags
-     * @return \stdClass
-     */
-    public static function map(array $definition, $flags = 0)
-    {
-        $tmp = new \stdClass();
-        $tmp->isMap = true;
-        $tmp->definition = $definition;
-        $tmp->flags = $flags;
-        return $tmp;
-    }
-
     /**
      * @param array|int $definition
      * @param int $flags
@@ -133,7 +127,7 @@ class Config
 
         if (!empty($unexpectedKeys)) {
             if (!self::$allowCustomOptions) {
-                trigger_error(sprintf('"%s" type definition: Non-standard keys "%s" ' . $suffix, $typeName, implode(', ', $unexpectedKeys)));
+                trigger_error(sprintf('Error in "%s" type definition: Non-standard keys "%s" ' . $suffix, $typeName, implode(', ', $unexpectedKeys)));
             }
             $map = array_intersect_key($map, $definitions);
         }
@@ -143,7 +137,7 @@ class Config
         $missingKeys = array_keys(array_diff_key($requiredKeys, $map));
         Utils::invariant(
             empty($missingKeys),
-            "Error in '$typeName' type definition: Required keys missing: '%s' $suffix", implode(', ', $missingKeys)
+            'Error in "' . $typeName . '" type definition: Required keys missing: "%s" %s', implode(', ', $missingKeys), $suffix
         );
 
         // Make sure that every map value is valid given the definition
@@ -163,30 +157,26 @@ class Config
     private static function validateEntry($typeName, $key, $value, $def, $pathStr)
     {
         $type = Utils::getVariableType($value);
-        $err = 'Error in "'.$typeName.'" type definition: expecting %s at "' . $pathStr . '", but got "' . $type . '"';
+        $err = 'Error in "'.$typeName.'" type definition: expecting "%s" at "' . $pathStr . '", but got "' . $type . '"';
 
         if ($def instanceof \stdClass) {
-            if ($def->flags & self::REQUIRED === 0 && $value === null) {
+            if (($def->flags & self::REQUIRED) === 0 && $value === null) {
                 return ;
             }
             if (($def->flags & self::MAYBE_THUNK) > 0) {
+                // TODO: consider wrapping thunk with other function to force validation of value returned by thunk
                 Utils::invariant(is_array($value) || is_callable($value), $err, 'array or callable');
             } else {
                 Utils::invariant(is_array($value), $err, 'array');
             }
 
-            if (!empty($def->isMap)) {
-                if ($def->flags & self::KEY_AS_NAME) {
-                    $value += ['name' => $key];
-                }
-                self::validateMap($typeName, $value, $def->definition, $pathStr);
-            } else if (!empty($def->isArray)) {
+            if (!empty($def->isArray)) {
 
                 if ($def->flags & self::REQUIRED) {
                     Utils::invariant(!empty($value), 'Error in "'.$typeName.'" type definition: ' . "Value at '$pathStr' cannot be empty array");
                 }
 
-                $err = 'Error in "'.$typeName.'" type definition: ' . "Each entry at '$pathStr' must be an array, but '%s' is '%s'";
+                $err = 'Error in "'.$typeName.'" type definition: ' . "Each entry at '$pathStr' must be an array, but entry at '%s' is '%s'";
 
                 foreach ($value as $arrKey => $arrValue) {
                     if (is_array($def->definition)) {
@@ -199,7 +189,7 @@ class Config
 
                         Utils::invariant(is_array($arrValue), $err, $arrKey, Utils::getVariableType($arrValue));
 
-                        if ($def->flags & self::KEY_AS_NAME) {
+                        if ($def->flags & self::KEY_AS_NAME && is_string($arrKey)) {
                             $arrValue += ['name' => $arrKey];
                         }
                         self::validateMap($typeName, $arrValue, $def->definition, "$pathStr:$arrKey");
@@ -214,7 +204,7 @@ class Config
             Utils::invariant(is_int($def), 'Error in "'.$typeName.'" type definition: ' . "Definition for '$pathStr' is expected to be single integer value");
 
             if ($def & self::REQUIRED) {
-                Utils::invariant($value !== null, 'Value at "%s" can not be null', $pathStr);
+                Utils::invariant($value !== null, 'Error in "'.$typeName.'" type definition: ' . 'Value at "%s" can not be null', $pathStr);
             }
 
             if (null === $value) {
@@ -234,7 +224,7 @@ class Config
                     Utils::invariant(is_numeric($value), $err, 'numeric');
                     break;
                 case $def & self::FLOAT:
-                    Utils::invariant(is_float($value), $err, 'float');
+                    Utils::invariant(is_float($value) || is_int($value), $err, 'float');
                     break;
                 case $def & self::INT:
                     Utils::invariant(is_int($value), $err, 'int');
@@ -246,6 +236,7 @@ class Config
                     Utils::invariant(is_scalar($value), $err, 'scalar');
                     break;
                 case $def & self::NAME:
+                    Utils::invariant(is_string($value), $err, 'name');
                     Utils::invariant(
                         preg_match('~^[_a-zA-Z][_a-zA-Z0-9]*$~', $value),
                         'Names must match /^[_a-zA-Z][_a-zA-Z0-9]*$/ but "%s" does not.',
@@ -256,28 +247,28 @@ class Config
                     Utils::invariant(
                         is_callable($value) || $value instanceof InputType,
                         $err,
-                        'callable or InputType definition'
+                        'InputType definition'
                     );
                     break;
                 case $def & self::OUTPUT_TYPE:
                     Utils::invariant(
                         is_callable($value) || $value instanceof OutputType,
                         $err,
-                        'callable or OutputType definition'
+                        'OutputType definition'
                     );
                     break;
                 case $def & self::INTERFACE_TYPE:
                     Utils::invariant(
                         is_callable($value) || $value instanceof InterfaceType,
                         $err,
-                        'callable or InterfaceType definition'
+                        'InterfaceType definition'
                     );
                     break;
                 case $def & self::OBJECT_TYPE:
                     Utils::invariant(
                         is_callable($value) || $value instanceof ObjectType,
                         $err,
-                        'callable or ObjectType definition'
+                        'ObjectType definition'
                     );
                     break;
                 default:
diff --git a/tests/Type/ConfigTest.php b/tests/Type/ConfigTest.php
new file mode 100644
index 0000000..82619f7
--- /dev/null
+++ b/tests/Type/ConfigTest.php
@@ -0,0 +1,676 @@
+<?php
+namespace Type;
+
+use GraphQL\Error\InvariantViolation;
+use GraphQL\Type\Definition\Config;
+use GraphQL\Type\Definition\EnumType;
+use GraphQL\Type\Definition\InputObjectType;
+use GraphQL\Type\Definition\InterfaceType;
+use GraphQL\Type\Definition\ObjectType;
+use GraphQL\Type\Definition\Type;
+
+class ConfigTest extends \PHPUnit_Framework_TestCase
+{
+    public static function tearDownAfterClass()
+    {
+        Config::disableValidation();
+    }
+
+    public function testToggling()
+    {
+        // Disabled by default
+        $this->assertEquals(false, Config::isValidationEnabled());
+        Config::validate(['test' => []], ['test' => Config::STRING]); // must not throw
+
+        Config::enableValidation();
+        $this->assertEquals(true, Config::isValidationEnabled());
+
+        try {
+            Config::validate(['test' => []], ['test' => Config::STRING]);
+            $this->fail('Expected exception not thrown');
+        } catch (\Exception $e) {
+        }
+
+        Config::disableValidation();
+        $this->assertEquals(false, Config::isValidationEnabled());
+        Config::validate(['test' => []], ['test' => Config::STRING]);
+    }
+
+    public function testValidateString()
+    {
+        $this->expectValidationPasses(
+            [
+                'test' => 'string',
+                'empty' => ''
+            ],
+            [
+                'test' => Config::STRING,
+                'empty' => Config::STRING
+            ]
+        );
+
+        $this->expectValidationThrows(
+            ['test' => 1],
+            ['test' => Config::STRING],
+            $this->typeError('expecting "string" at "test", but got "integer"')
+        );
+    }
+
+    public function testArray()
+    {
+        $this->expectValidationPasses(
+            ['test' => [
+                [],
+                ['nested' => 'A'],
+                ['nested' => null]
+            ]],
+            ['test' => Config::arrayOf(
+                ['nested' => Config::STRING]
+            )]
+        );
+
+        $this->expectValidationThrows(
+            ['test' => [
+                null
+            ]],
+            ['test' => Config::arrayOf(
+                ['nested' => Config::STRING]
+            )],
+            $this->typeError("Each entry at 'test' must be an array, but entry at '0' is 'NULL'")
+        );
+
+        $this->expectValidationPasses(
+            ['test' => null],
+            ['test' => Config::arrayOf(
+                ['nested' => Config::STRING]
+            )]
+        );
+
+        $this->expectValidationThrows(
+            ['test' => null],
+            ['test' => Config::arrayOf(
+                ['nested' => Config::STRING],
+                Config::REQUIRED
+            )],
+            $this->typeError('expecting "array" at "test", but got "NULL"')
+        );
+
+        // Check validation nesting:
+        $this->expectValidationPasses(
+            ['nest' => [
+                ['nest' => [
+                    ['test' => 'value']
+                ]]
+            ]],
+            ['nest' => Config::arrayOf([
+                'nest' => Config::arrayOf([
+                    'test' => Config::STRING
+                ])
+            ])]
+        );
+
+        $this->expectValidationThrows(
+            ['nest' => [
+                ['nest' => [
+                    ['test' => 'notInt']
+                ]]
+            ]],
+            ['nest' => Config::arrayOf([
+                'nest' => Config::arrayOf([
+                    'test' => Config::INT
+                ])
+            ])],
+            $this->typeError('expecting "int" at "nest:0:nest:0:test", but got "string"')
+        );
+
+        // Check arrays of types:
+        $this->expectValidationPasses(
+            ['nest' => [
+                Type::string(),
+                Type::int()
+            ]],
+            ['nest' => Config::arrayOf(
+                Config::OUTPUT_TYPE, Config::REQUIRED
+            )]
+        );
+
+        // Check arrays of types:
+        $this->expectValidationThrows(
+            ['nest' => [
+                Type::string(),
+                new InputObjectType(['name' => 'test', 'fields' => []])
+            ]],
+            ['nest' => Config::arrayOf(
+                Config::OUTPUT_TYPE, Config::REQUIRED
+            )],
+            $this->typeError('expecting "OutputType definition" at "nest:1", but got "test"')
+        );
+    }
+
+    public function testRequired()
+    {
+        $this->expectValidationPasses(
+            ['required' => ''],
+            ['required' => Config::STRING | Config::REQUIRED]
+        );
+
+        $this->expectValidationThrows(
+            [],
+            ['required' => Config::STRING | Config::REQUIRED],
+            $this->typeError('Required keys missing: "required" ')
+        );
+
+        $this->expectValidationThrows(
+            ['required' => null],
+            ['required' => Config::STRING | Config::REQUIRED],
+            $this->typeError('Value at "required" can not be null')
+        );
+
+        $this->expectValidationPasses(
+            ['test' => [
+                ['nested' => '']
+            ]],
+            ['test' => Config::arrayOf([
+                'nested' => Config::STRING | Config::REQUIRED
+            ])]
+        );
+
+        $this->expectValidationThrows(
+            ['test' => [
+                []
+            ]],
+            ['test' => Config::arrayOf([
+                'nested' => Config::STRING | Config::REQUIRED
+            ])],
+            $this->typeError('Required keys missing: "nested"  at test:0')
+        );
+
+        $this->expectValidationThrows(
+            ['test' => [
+                ['nested' => null]
+            ]],
+            ['test' => Config::arrayOf([
+                'nested' => Config::STRING | Config::REQUIRED
+            ])],
+            $this->typeError('Value at "test:0:nested" can not be null')
+        );
+
+        $this->expectValidationPasses(
+            ['test' => [
+                ['nested' => null]
+            ]],
+            ['test' => Config::arrayOf(
+                ['nested' => Config::STRING],
+                Config::REQUIRED
+            )]
+        );
+
+        $this->expectValidationThrows(
+            ['test' => [
+
+            ]],
+            ['test' => Config::arrayOf(
+                ['nested' => Config::STRING],
+                Config::REQUIRED
+            )],
+            $this->typeError("Value at 'test' cannot be empty array")
+        );
+    }
+
+    public function testKeyAsName()
+    {
+        $this->expectValidationPasses(
+            ['test' => [
+                'name1' => ['key1' => null],
+                ['name' => 'name1'],
+            ]],
+            ['test' => Config::arrayOf(
+                ['name' => Config::STRING | Config::REQUIRED, 'key1' => Config::STRING],
+                Config::KEY_AS_NAME
+            )]
+        );
+
+        $this->expectValidationThrows(
+            ['test' => [
+                'name1' => ['key1' => null]
+            ]],
+            ['test' => Config::arrayOf(
+                ['name' => Config::STRING | Config::REQUIRED, 'key1' => Config::STRING]
+            )],
+            $this->typeError('Required keys missing: "name"  at test:name1')
+        );
+
+        $this->expectValidationThrows(
+            ['test' => [
+                ['key1' => null]
+            ]],
+            ['test' => Config::arrayOf(
+                ['name' => Config::STRING | Config::REQUIRED, 'key1' => Config::STRING],
+                Config::KEY_AS_NAME
+            )],
+            $this->typeError('Required keys missing: "name"  at test:0')
+        );
+    }
+
+    public function testMaybeThunk()
+    {
+        $this->expectValidationPasses(
+            [
+                'test' => [
+                    ['nested' => ''],
+                    ['nested' => '1'],
+                ],
+                'testThunk' => function() {
+                    // Currently config won't validate thunk return value
+                }
+            ],
+            [
+                'test' => Config::arrayOf(
+                    ['nested' => Config::STRING | Config::REQUIRED],
+                    Config::MAYBE_THUNK
+                ),
+                'testThunk' => Config::arrayOf(
+                    ['nested' => Config::STRING | Config::REQUIRED],
+                    Config::MAYBE_THUNK
+                )
+            ]
+        );
+
+        $this->expectValidationThrows(
+            [
+                'testThunk' => function() {
+
+                }
+            ],
+            [
+                'testThunk' => Config::arrayOf(
+                    ['nested' => Config::STRING | Config::REQUIRED]
+                )
+            ],
+            $this->typeError('expecting "array" at "testThunk", but got "Closure"')
+        );
+
+        $this->expectValidationThrows(
+            [
+                'testThunk' => 1
+            ],
+            [
+                'testThunk' => Config::arrayOf(
+                    ['nested' => Config::STRING | Config::REQUIRED],
+                    Config::MAYBE_THUNK
+                )
+            ],
+            $this->typeError('expecting "array or callable" at "testThunk", but got "integer"')
+        );
+    }
+
+    public function testMaybeType()
+    {
+        $type = new ObjectType([
+            'name' => 'Test',
+            'fields' => []
+        ]);
+
+        $this->expectValidationPasses(
+            ['test' => [
+                $type,
+                ['type' => $type],
+            ]],
+            ['test' => Config::arrayOf(
+                ['type' => Config::OBJECT_TYPE | Config::REQUIRED],
+                Config::MAYBE_TYPE
+            )]
+        );
+
+        $this->expectValidationThrows(
+            ['test' => [
+                ['type' => 'str']
+            ]],
+            ['test' => Config::arrayOf(
+                ['type' => Config::OBJECT_TYPE | Config::REQUIRED],
+                Config::MAYBE_TYPE
+            )],
+            $this->typeError('expecting "ObjectType definition" at "test:0:type", but got "string"')
+        );
+
+        $this->expectValidationThrows(
+            ['test' => [
+                $type
+            ]],
+            ['test' => Config::arrayOf(
+                ['name' => Config::OBJECT_TYPE | Config::REQUIRED]
+            )],
+            $this->typeError("Each entry at 'test' must be an array, but entry at '0' is 'Test'")
+        );
+    }
+
+    public function testMaybeName()
+    {
+        $this->expectValidationPasses(
+            ['test' => [
+                'some-name',
+                ['name' => 'other-name'],
+            ]],
+            ['test' => Config::arrayOf(
+                ['name' => Config::STRING | Config::REQUIRED],
+                Config::MAYBE_NAME
+            )]
+        );
+
+        $this->expectValidationThrows(
+            ['test' => [
+                'some-name'
+            ]],
+            ['test' => Config::arrayOf(
+                ['name' => Config::OBJECT_TYPE | Config::REQUIRED]
+            )],
+            $this->typeError("Each entry at 'test' must be an array, but entry at '0' is 'string'")
+        );
+
+        $this->expectValidationPasses(
+            ['test' => [
+                'some-key' => 'some-name',
+                'some-name'
+            ]],
+            ['test' => Config::arrayOf(
+                ['name' => Config::STRING | Config::REQUIRED],
+                Config::MAYBE_NAME | Config::KEY_AS_NAME
+            )]
+        );
+    }
+
+    public function getValidValues()
+    {
+        return [
+            // $type, $validValue
+            [Config::ANY, null],
+            [Config::ANY, 0],
+            [Config::ANY, ''],
+            [Config::ANY, '0'],
+            [Config::ANY, 1],
+            [Config::ANY, function() {}],
+            [Config::ANY, []],
+            [Config::ANY, new \stdClass()],
+            [Config::STRING, null],
+            [Config::STRING, ''],
+            [Config::STRING, '0'],
+            [Config::STRING, 'anything'],
+            [Config::BOOLEAN, null],
+            [Config::BOOLEAN, false],
+            [Config::BOOLEAN, true],
+            [Config::INT, null],
+            [Config::INT, 0],
+            [Config::INT, 1],
+            [Config::INT, -1],
+            [Config::INT, 5000000],
+            [Config::INT, -5000000],
+            [Config::FLOAT, null],
+            [Config::FLOAT, 0],
+            [Config::FLOAT, 0.0],
+            [Config::FLOAT, 0.1],
+            [Config::FLOAT, -12.5],
+            [Config::NUMERIC, null],
+            [Config::NUMERIC, '0'],
+            [Config::NUMERIC, 0],
+            [Config::NUMERIC, 1],
+            [Config::NUMERIC, 0.0],
+            [Config::NUMERIC, 1.0],
+            [Config::NUMERIC, -1.0],
+            [Config::NUMERIC, -1],
+            [Config::NUMERIC, 1],
+            [Config::CALLBACK, null],
+            [Config::CALLBACK, function() {}],
+            [Config::CALLBACK, [$this, 'getValidValues']],
+            [Config::SCALAR, null],
+            [Config::SCALAR, 0],
+            [Config::SCALAR, 1],
+            [Config::SCALAR, 0.0],
+            [Config::SCALAR, 1.0],
+            [Config::SCALAR, true],
+            [Config::SCALAR, false],
+            [Config::SCALAR, ''],
+            [Config::SCALAR, '0'],
+            [Config::SCALAR, 'anything'],
+            [Config::NAME, null],
+            [Config::NAME, 'CamelCaseIsOk'],
+            [Config::NAME, 'underscore_is_ok'],
+            [Config::NAME, 'numbersAreOk0123456789'],
+            [Config::INPUT_TYPE, null],
+            [Config::INPUT_TYPE, new InputObjectType(['name' => 'test', 'fields' => []])],
+            [Config::INPUT_TYPE, new EnumType(['name' => 'test2', 'values' => ['A', 'B', 'C']])],
+            [Config::INPUT_TYPE, Type::string()],
+            [Config::INPUT_TYPE, Type::int()],
+            [Config::INPUT_TYPE, Type::float()],
+            [Config::INPUT_TYPE, Type::boolean()],
+            [Config::INPUT_TYPE, Type::id()],
+            [Config::INPUT_TYPE, Type::listOf(Type::string())],
+            [Config::INPUT_TYPE, Type::nonNull(Type::string())],
+            [Config::OUTPUT_TYPE, null],
+            [Config::OUTPUT_TYPE, new ObjectType(['name' => 'test3', 'fields' => []])],
+            [Config::OUTPUT_TYPE, new EnumType(['name' => 'test4', 'values' => ['A', 'B', 'C']])],
+            [Config::OUTPUT_TYPE, Type::string()],
+            [Config::OUTPUT_TYPE, Type::int()],
+            [Config::OUTPUT_TYPE, Type::float()],
+            [Config::OUTPUT_TYPE, Type::boolean()],
+            [Config::OUTPUT_TYPE, Type::id()],
+            [Config::OBJECT_TYPE, null],
+            [Config::OBJECT_TYPE, new ObjectType(['name' => 'test6', 'fields' => []])],
+            [Config::INTERFACE_TYPE, null],
+            [Config::INTERFACE_TYPE, new InterfaceType(['name' => 'test7', 'fields' => []])],
+        ];
+    }
+
+    /**
+     * @dataProvider getValidValues
+     */
+    public function testValidValues($type, $validValue)
+    {
+        $this->expectValidationPasses(
+            ['test' => $validValue],
+            ['test' => $type]
+        );
+    }
+
+    public function getInvalidValues()
+    {
+        return [
+            // $type, $typeLabel, $invalidValue, $actualTypeLabel
+            [Config::STRING, 'string', 1, 'integer'],
+            [Config::STRING, 'string', 0, 'integer'],
+            [Config::STRING, 'string', false, 'boolean'],
+            [Config::STRING, 'string', function() {}, 'Closure'],
+            [Config::STRING, 'string', [], 'array'],
+            [Config::STRING, 'string', new \stdClass(), 'stdClass'],
+            [Config::BOOLEAN, 'boolean', '', 'string'],
+            [Config::BOOLEAN, 'boolean', 1, 'integer'],
+            [Config::BOOLEAN, 'boolean', function() {}, 'Closure'],
+            [Config::BOOLEAN, 'boolean', [], 'array'],
+            [Config::BOOLEAN, 'boolean', new \stdClass(), 'stdClass'],
+            [Config::INT, 'int', false, 'boolean'],
+            [Config::INT, 'int', '', 'string'],
+            [Config::INT, 'int', '0', 'string'],
+            [Config::INT, 'int', '1', 'string'],
+            [Config::INT, 'int', function() {}, 'Closure'],
+            [Config::INT, 'int', [], 'array'],
+            [Config::INT, 'int', new \stdClass(), 'stdClass'],
+            [Config::FLOAT, 'float', '', 'string'],
+            [Config::FLOAT, 'float', '0', 'string'],
+            [Config::FLOAT, 'float', function() {}, 'Closure'],
+            [Config::FLOAT, 'float', [], 'array'],
+            [Config::FLOAT, 'float', new \stdClass(), 'stdClass'],
+            [Config::NUMERIC, 'numeric', '', 'string'],
+            [Config::NUMERIC, 'numeric', 'tmp', 'string'],
+            [Config::NUMERIC, 'numeric', [], 'array'],
+            [Config::NUMERIC, 'numeric', new \stdClass(), 'stdClass'],
+            [Config::NUMERIC, 'numeric', function() {}, 'Closure'],
+            [Config::CALLBACK, 'callable', 1, 'integer'],
+            [Config::CALLBACK, 'callable', '', 'string'],
+            [Config::CALLBACK, 'callable', [], 'array'],
+            [Config::CALLBACK, 'callable', new \stdClass(), 'stdClass'],
+            [Config::SCALAR, 'scalar', [], 'array'],
+            [Config::SCALAR, 'scalar', new \stdClass(), 'stdClass'],
+            [Config::SCALAR, 'scalar', function() {}, 'Closure'],
+            [Config::NAME, 'name', 5, 'integer'],
+            [Config::NAME, 'name', function() {}, 'Closure'],
+            [Config::NAME, 'name', [], 'array'],
+            [Config::NAME, 'name', new \stdClass(), 'stdClass'],
+            [Config::NAME, 'name', '', null, 'Names must match /^[_a-zA-Z][_a-zA-Z0-9]*$/ but "" does not.'],
+            [Config::NAME, 'name', '0', null, 'Names must match /^[_a-zA-Z][_a-zA-Z0-9]*$/ but "0" does not.'],
+            [Config::NAME, 'name', '4abc', null, 'Names must match /^[_a-zA-Z][_a-zA-Z0-9]*$/ but "4abc" does not.'],
+            [Config::NAME, 'name', 'specialCharsAreBad!', null, 'Names must match /^[_a-zA-Z][_a-zA-Z0-9]*$/ but "specialCharsAreBad!" does not.'],
+            [Config::INPUT_TYPE, 'InputType definition', new ObjectType(['name' => 'test3', 'fields' => []]), 'test3'],
+            [Config::INPUT_TYPE, 'InputType definition', '', 'string'],
+            [Config::INPUT_TYPE, 'InputType definition', 'test', 'string'],
+            [Config::INPUT_TYPE, 'InputType definition', 1, 'integer'],
+            [Config::INPUT_TYPE, 'InputType definition', 0.5, 'double'],
+            [Config::INPUT_TYPE, 'InputType definition', false, 'boolean'],
+            [Config::INPUT_TYPE, 'InputType definition', [], 'array'],
+            [Config::INPUT_TYPE, 'InputType definition', new \stdClass(), 'stdClass'],
+            [Config::OUTPUT_TYPE, 'OutputType definition', new InputObjectType(['name' => 'InputTypeTest']), 'InputTypeTest'],
+            [Config::OBJECT_TYPE, 'ObjectType definition', '', 'string'],
+            [Config::OBJECT_TYPE, 'ObjectType definition', new InputObjectType(['name' => 'InputTypeTest2']), 'InputTypeTest2'],
+            [Config::INTERFACE_TYPE, 'InterfaceType definition', new ObjectType(['name' => 'ObjectTypeTest']), 'ObjectTypeTest'],
+            [Config::INTERFACE_TYPE, 'InterfaceType definition', 'InputTypeTest2', 'string'],
+        ];
+    }
+
+    /**
+     * @dataProvider getInvalidValues
+     */
+    public function testInvalidValues($type, $typeLabel, $invalidValue, $actualTypeLabel = null, $expectedFullError = null)
+    {
+        if (!$expectedFullError) {
+            $expectedFullError = $this->typeError(
+                $invalidValue === null ?
+                    'Value at "test" can not be null' :
+                    'expecting "' . $typeLabel . '" at "test", but got "' . $actualTypeLabel . '"'
+            );
+        }
+
+        $this->expectValidationThrows(
+            ['test' => $invalidValue],
+            ['test' => $type],
+            $expectedFullError
+        );
+    }
+
+    public function testErrorMessageContainsTypeName()
+    {
+        $this->expectValidationThrows(
+            [
+                'name' => 'TypeName',
+                'test' => 'notInt'
+            ],
+            [
+                'name' => Config::STRING | Config::REQUIRED,
+                'test' => Config::INT
+            ],
+            $this->typeError('expecting "int" at "test", but got "string"', 'TypeName')
+        );
+    }
+
+    public function testValidateField()
+    {
+        Config::enableValidation();
+
+        // Should just validate:
+        Config::validateField(
+            'TypeName',
+            ['test' => 'value'],
+            ['test' => Config::STRING]
+        );
+
+        // Should include type name in error
+        try {
+            Config::validateField(
+                'TypeName',
+                ['test' => 'notInt'],
+                ['test' => Config::INT]
+            );
+            $this->fail('Expected exception not thrown');
+        } catch (InvariantViolation $e) {
+            $this->assertEquals(
+                $this->typeError('expecting "int" at "(Unknown Field):test", but got "string"', 'TypeName'),
+                $e->getMessage()
+            );
+        }
+
+        // Should include field type in error when field name is unknown:
+        try {
+            Config::validateField(
+                'TypeName',
+                ['type' => Type::string()],
+                ['name' => Config::STRING | Config::REQUIRED, 'type' => Config::OUTPUT_TYPE]
+            );
+            $this->fail('Expected exception not thrown');
+        } catch (InvariantViolation $e) {
+            $this->assertEquals(
+                $this->typeError('Required keys missing: "name"  at (Unknown Field of type: String)', 'TypeName'),
+                $e->getMessage()
+            );
+        }
+
+        // Should include field name in error when field name is set:
+        try {
+            Config::validateField(
+                'TypeName',
+                ['name' => 'fieldName', 'test' => 'notInt'],
+                ['name' => Config::STRING, 'test' => Config::INT]
+            );
+            $this->fail('Expected exception not thrown');
+        } catch (InvariantViolation $e) {
+            $this->assertEquals(
+                $this->typeError('expecting "int" at "test", but got "string"', 'TypeName'),
+                $e->getMessage()
+            );
+        }
+    }
+
+    public function testAllowCustomOptions()
+    {
+        // Disabled by default when validation is enabled
+        Config::enableValidation(true);
+
+        Config::validate(
+            ['test' => 'value', 'test2' => 'value'],
+            ['test' => Config::STRING]
+        );
+
+        Config::enableValidation(false);
+
+        try {
+            Config::validate(
+                ['test' => 'value', 'test2' => 'value'],
+                ['test' => Config::STRING]
+            );
+            $this->fail('Expected exception not thrown');
+        } catch (\PHPUnit_Framework_Error_Notice $e) {
+            $this->assertEquals(
+                $this->typeError('Non-standard keys "test2" '),
+                $e->getMessage()
+            );
+        }
+    }
+
+    private function expectValidationPasses($config, $definition)
+    {
+        Config::enableValidation(false);
+        Config::validate($config, $definition);
+    }
+
+    private function expectValidationThrows($config, $definition, $expectedError)
+    {
+        Config::enableValidation(false);
+        try {
+            Config::validate($config, $definition);
+            $this->fail('Expected exception not thrown: ' . $expectedError);
+        } catch (InvariantViolation $e) {
+            $this->assertEquals($expectedError, $e->getMessage());
+        }
+    }
+
+    private function typeError($err, $typeName = null)
+    {
+        return 'Error in "'. ($typeName ?: '(Unnamed Type)') . '" type definition: ' . $err;
+    }
+}
diff --git a/tests/Type/DefinitionTest.php b/tests/Type/DefinitionTest.php
index 7ddb808..a39e933 100644
--- a/tests/Type/DefinitionTest.php
+++ b/tests/Type/DefinitionTest.php
@@ -469,7 +469,7 @@ class DefinitionTest extends \PHPUnit_Framework_TestCase
                 $this->fail('Expected exception not thrown');
             } catch (\Exception $e) {
                 $this->assertSame(
-                    'Error in "BadUnion" type definition: expecting callable or ObjectType definition at "types:0", but got "' . Utils::getVariableType($type) . '"',
+                    'Error in "BadUnion" type definition: expecting "ObjectType definition" at "types:0", but got "' . Utils::getVariableType($type) . '"',
                     $e->getMessage()
                 );
             }
diff --git a/tests/Type/SchemaValidatorTest.php b/tests/Type/SchemaValidatorTest.php
index 67bf0bf..78384ef 100644
--- a/tests/Type/SchemaValidatorTest.php
+++ b/tests/Type/SchemaValidatorTest.php
@@ -2,6 +2,7 @@
 namespace GraphQL\Tests\Type;
 
 use GraphQL\Schema;
+use GraphQL\Type\Definition\Config;
 use GraphQL\Type\Definition\CustomScalarType;
 use GraphQL\Type\Definition\EnumType;
 use GraphQL\Type\Definition\InputObjectType;
@@ -392,6 +393,9 @@ class SchemaValidatorTest extends \PHPUnit_Framework_TestCase
 
     public function testRejectsASchemaThatUsesAnInputTypeAsAField()
     {
+        $enabled = Config::isValidationEnabled();
+        Config::disableValidation();
+
         $kinds = [
             'GraphQL\Type\Definition\ObjectType',
         ];
@@ -415,6 +419,10 @@ class SchemaValidatorTest extends \PHPUnit_Framework_TestCase
                 $validationResult[0]->message
             );
         }
+
+        if ($enabled) {
+            Config::enableValidation();
+        }
     }
 
     public function testAcceptsASchemaThatSimplyHasAnInputTypeAsAFieldArg()