diff --git a/src/Error/ClientAware.php b/src/Error/ClientAware.php
index 26ab969..df69d14 100644
--- a/src/Error/ClientAware.php
+++ b/src/Error/ClientAware.php
@@ -14,4 +14,13 @@ interface ClientAware
      * @return bool
      */
     public function isClientSafe();
+
+    /**
+     * Returns string describing error category.
+     *
+     * Value "graphql" is reserved for errors produced by query parsing or validation, do not use it.
+     *
+     * @return string
+     */
+    public function getCategory();
 }
diff --git a/src/Error/Error.php b/src/Error/Error.php
index 3677298..e2f3b81 100644
--- a/src/Error/Error.php
+++ b/src/Error/Error.php
@@ -16,6 +16,9 @@ use GraphQL\Utils\Utils;
  */
 class Error extends \Exception implements \JsonSerializable, ClientAware
 {
+    const GRAPHQL = 'graphql';
+    const INTERNAL = 'internal';
+
     /**
      * A message describing the Error for debugging purposes.
      *
@@ -67,6 +70,11 @@ class Error extends \Exception implements \JsonSerializable, ClientAware
      */
     private $isClientSafe;
 
+    /**
+     * @var string
+     */
+    protected $category;
+
     /**
      * Given an arbitrary Error, presumably thrown while attempting to execute a
      * GraphQL operation, produce a new GraphQLError aware of the location in the
@@ -131,7 +139,14 @@ class Error extends \Exception implements \JsonSerializable, ClientAware
      * @param array|null $path
      * @param \Throwable $previous
      */
-    public function __construct($message, $nodes = null, Source $source = null, $positions = null, $path = null, $previous = null)
+    public function __construct(
+        $message,
+        $nodes = null,
+        Source $source = null,
+        $positions = null,
+        $path = null,
+        $previous = null
+    )
     {
         parent::__construct($message, 0, $previous);
 
@@ -146,21 +161,32 @@ class Error extends \Exception implements \JsonSerializable, ClientAware
 
         if ($previous instanceof ClientAware) {
             $this->isClientSafe = $previous->isClientSafe();
-        } else if ($previous === null) {
-            $this->isClientSafe = true;
-        } else {
+            $this->category = $previous->getCategory() ?: static::INTERNAL;
+        } else if ($previous) {
             $this->isClientSafe = false;
+            $this->category = static::INTERNAL;
+        } else {
+            $this->isClientSafe = true;
+            $this->category = static::GRAPHQL;
         }
     }
 
     /**
-     * @return bool
+     * @inheritdoc
      */
     public function isClientSafe()
     {
         return $this->isClientSafe;
     }
 
+    /**
+     * @inheritdoc
+     */
+    public function getCategory()
+    {
+        return $this->category;
+    }
+
     /**
      * @return Source|null
      */
@@ -222,7 +248,7 @@ class Error extends \Exception implements \JsonSerializable, ClientAware
     public function toSerializableArray()
     {
         $arr = [
-            'message' => $this->getMessage(),
+            'message' => $this->getMessage()
         ];
 
         $locations = Utils::map($this->getLocations(), function(SourceLocation $loc) {
diff --git a/src/Error/FormattedError.php b/src/Error/FormattedError.php
index 42605ee..395216b 100644
--- a/src/Error/FormattedError.php
+++ b/src/Error/FormattedError.php
@@ -44,18 +44,19 @@ class FormattedError
         if ($e instanceof ClientAware) {
             if ($e->isClientSafe()) {
                 $result = [
-                    'message' => $e->getMessage()
+                    'message' => $e->getMessage(),
+                    'category' => $e->getCategory()
                 ];
             } else {
                 $result = [
                     'message' => $internalErrorMessage,
-                    'isInternalError' => true
+                    'category' => $e->getCategory()
                 ];
             }
         } else {
             $result = [
                 'message' => $internalErrorMessage,
-                'isInternalError' => true
+                'category' => Error::INTERNAL
             ];
         }
         if (($debug & self::INCLUDE_DEBUG_MESSAGE > 0) && $result['message'] === $internalErrorMessage) {
diff --git a/src/Error/UserError.php b/src/Error/UserError.php
index bf283a5..5a4b38c 100644
--- a/src/Error/UserError.php
+++ b/src/Error/UserError.php
@@ -4,7 +4,7 @@ namespace GraphQL\Error;
 /**
  * Class UserError
  *
- * Error caused by actions of GraphQL clients. Can be safely displayed to client...
+ * Error caused by actions of GraphQL clients. Can be safely displayed to a client...
  *
  * @package GraphQL\Error
  */
@@ -17,4 +17,12 @@ class UserError extends \RuntimeException implements ClientAware
     {
         return true;
     }
+
+    /**
+     * @return string
+     */
+    public function getCategory()
+    {
+        return 'user';
+    }
 }
diff --git a/src/Server/Helper.php b/src/Server/Helper.php
index de15317..610b26e 100644
--- a/src/Server/Helper.php
+++ b/src/Server/Helper.php
@@ -98,7 +98,7 @@ class Helper
 
             $operationType = AST::getOperation($doc, $op->operation);
             if ($op->isReadOnly() && $operationType !== 'query') {
-                throw new Error("GET supports only query operation");
+                throw new RequestError("GET supports only query operation");
             }
 
             $validationErrors = DocumentValidator::validate(
@@ -123,6 +123,10 @@ class Helper
                     $config->getDefaultFieldResolver()
                 );
             }
+        } catch (RequestError $e) {
+            $result = $promiseAdapter->createFulfilled(
+                new ExecutionResult(null, [Error::createLocatedError($e)])
+            );
         } catch (Error $e) {
             $result = $promiseAdapter->createFulfilled(
                 new ExecutionResult(null, [$e])
@@ -159,7 +163,7 @@ class Helper
         $loader = $config->getPersistentQueryLoader();
 
         if (!$loader) {
-            throw new Error("Persisted queries are not supported by this server");
+            throw new RequestError("Persisted queries are not supported by this server");
         }
 
         $source = $loader($op->queryId, $op);
@@ -266,10 +270,10 @@ class Helper
                 $bodyParams = json_decode($rawBody ?: '', true);
 
                 if (json_last_error()) {
-                    throw new Error("Could not parse JSON: " . json_last_error_msg());
+                    throw new RequestError("Could not parse JSON: " . json_last_error_msg());
                 }
                 if (!is_array($bodyParams)) {
-                    throw new Error(
+                    throw new RequestError(
                         "GraphQL Server expects JSON object or array, but got " .
                         Utils::printSafeJson($bodyParams)
                     );
@@ -277,9 +281,9 @@ class Helper
             } else if (stripos($contentType, 'application/x-www-form-urlencoded') !== false) {
                 $bodyParams = $_POST;
             } else if (null === $contentType) {
-                throw new Error('Missing "Content-Type" header');
+                throw new RequestError('Missing "Content-Type" header');
             } else {
-                throw new Error("Unexpected content type: " . Utils::printSafeJson($contentType));
+                throw new RequestError("Unexpected content type: " . Utils::printSafeJson($contentType));
             }
         }
 
@@ -395,7 +399,7 @@ class Helper
                 $result = OperationParams::create($bodyParams);
             }
         } else {
-            throw new Error('HTTP Method "' . $method . '" is not supported');
+            throw new RequestError('HTTP Method "' . $method . '" is not supported');
         }
         return $result;
     }
@@ -418,33 +422,33 @@ class Helper
     {
         $errors = [];
         if (!$params->query && !$params->queryId) {
-            $errors[] = new Error('GraphQL Request must include at least one of those two parameters: "query" or "queryId"');
+            $errors[] = new RequestError('GraphQL Request must include at least one of those two parameters: "query" or "queryId"');
         }
         if ($params->query && $params->queryId) {
-            $errors[] = new Error('GraphQL Request parameters "query" and "queryId" are mutually exclusive');
+            $errors[] = new RequestError('GraphQL Request parameters "query" and "queryId" are mutually exclusive');
         }
 
         if ($params->query !== null && (!is_string($params->query) || empty($params->query))) {
-            $errors[] = new Error(
+            $errors[] = new RequestError(
                 'GraphQL Request parameter "query" must be string, but got ' .
                 Utils::printSafeJson($params->query)
             );
         }
         if ($params->queryId !== null && (!is_string($params->queryId) || empty($params->queryId))) {
-            $errors[] = new Error(
+            $errors[] = new RequestError(
                 'GraphQL Request parameter "queryId" must be string, but got ' .
                 Utils::printSafeJson($params->queryId)
             );
         }
 
         if ($params->operation !== null && (!is_string($params->operation) || empty($params->operation))) {
-            $errors[] = new Error(
+            $errors[] = new RequestError(
                 'GraphQL Request parameter "operation" must be string, but got ' .
                 Utils::printSafeJson($params->operation)
             );
         }
         if ($params->variables !== null && (!is_array($params->variables) || isset($params->variables[0]))) {
-            $errors[] = new Error(
+            $errors[] = new RequestError(
                 'GraphQL Request parameter "variables" must be object or JSON string parsed to object, but got ' .
                 Utils::printSafeJson($params->getOriginalInput('variables'))
             );
diff --git a/src/Server/RequestError.php b/src/Server/RequestError.php
new file mode 100644
index 0000000..d07f527
--- /dev/null
+++ b/src/Server/RequestError.php
@@ -0,0 +1,29 @@
+<?php
+namespace GraphQL\Server;
+
+use GraphQL\Error\ClientAware;
+
+class RequestError extends \Exception implements ClientAware
+{
+    /**
+     * Returns true when exception message is safe to be displayed to client
+     *
+     * @return bool
+     */
+    public function isClientSafe()
+    {
+        return true;
+    }
+
+    /**
+     * Returns string describing error category. E.g. "validation" for your own validation errors.
+     *
+     * Value "graphql" is reserved for errors produced by query parsing or validation, do not use it.
+     *
+     * @return string
+     */
+    public function getCategory()
+    {
+        return 'request';
+    }
+}
diff --git a/tests/Executor/AbstractPromiseTest.php b/tests/Executor/AbstractPromiseTest.php
index 61347a1..8925b05 100644
--- a/tests/Executor/AbstractPromiseTest.php
+++ b/tests/Executor/AbstractPromiseTest.php
@@ -186,7 +186,7 @@ class AbstractPromiseTest extends \PHPUnit_Framework_TestCase
                 [
                     'message' => 'We are testing this error',
                     'locations' => [['line' => 2, 'column' => 7]],
-                    'path' => ['pets', 0]
+                    'path' => ['pets', 0],
                 ],
                 [
                     'message' => 'We are testing this error',
@@ -196,7 +196,7 @@ class AbstractPromiseTest extends \PHPUnit_Framework_TestCase
             ]
         ];
 
-        $this->assertEquals($expected, $result);
+        $this->assertArraySubset($expected, $result);
     }
 
     /**
@@ -380,7 +380,7 @@ class AbstractPromiseTest extends \PHPUnit_Framework_TestCase
             ]
         ];
 
-        $this->assertEquals($expected, $result);
+        $this->assertArraySubset($expected, $result);
     }
 
     /**
@@ -481,7 +481,7 @@ class AbstractPromiseTest extends \PHPUnit_Framework_TestCase
             ]
         ];
 
-        $this->assertEquals($expected, $result);
+        $this->assertArraySubset($expected, $result);
     }
 
     /**
@@ -655,6 +655,6 @@ class AbstractPromiseTest extends \PHPUnit_Framework_TestCase
             ]
         ];
 
-        $this->assertEquals($expected, $result);
+        $this->assertArraySubset($expected, $result);
     }
 }
diff --git a/tests/Executor/AbstractTest.php b/tests/Executor/AbstractTest.php
index 1bb2ecb..024a5bf 100644
--- a/tests/Executor/AbstractTest.php
+++ b/tests/Executor/AbstractTest.php
@@ -274,7 +274,7 @@ class AbstractTest extends \PHPUnit_Framework_TestCase
         ];
         $actual = GraphQL::execute($schema, $query);
 
-        $this->assertEquals($expected, $actual);
+        $this->assertArraySubset($expected, $actual);
     }
 
     /**
@@ -369,7 +369,7 @@ class AbstractTest extends \PHPUnit_Framework_TestCase
                 'path' => ['pets', 2]
             ]]
         ];
-        $this->assertEquals($expected, $result);
+        $this->assertArraySubset($expected, $result);
     }
 
     /**
diff --git a/tests/Executor/ExecutorTest.php b/tests/Executor/ExecutorTest.php
index 24120de..5e62935 100644
--- a/tests/Executor/ExecutorTest.php
+++ b/tests/Executor/ExecutorTest.php
@@ -522,7 +522,7 @@ class ExecutorTest extends \PHPUnit_Framework_TestCase
 
         $result = Executor::execute($schema, $docAst, $data)->toArray();
 
-        $this->assertEquals($expected, $result);
+        $this->assertArraySubset($expected, $result);
     }
 
     /**
@@ -615,7 +615,7 @@ class ExecutorTest extends \PHPUnit_Framework_TestCase
             ]
         ];
 
-        $this->assertEquals($expected, $result->toArray());
+        $this->assertArraySubset($expected, $result->toArray());
     }
 
     /**
@@ -645,7 +645,7 @@ class ExecutorTest extends \PHPUnit_Framework_TestCase
             ]
         ];
 
-        $this->assertEquals($expected, $result->toArray());
+        $this->assertArraySubset($expected, $result->toArray());
     }
 
     /**
@@ -683,7 +683,7 @@ class ExecutorTest extends \PHPUnit_Framework_TestCase
 
         ];
 
-        $this->assertEquals($expected, $result->toArray());
+        $this->assertArraySubset($expected, $result->toArray());
     }
 
     /**
@@ -996,7 +996,7 @@ class ExecutorTest extends \PHPUnit_Framework_TestCase
             ]
         ];
 
-        $this->assertEquals($expected, $result->toArray());
+        $this->assertArraySubset($expected, $result->toArray());
     }
 
     /**
diff --git a/tests/Executor/VariablesTest.php b/tests/Executor/VariablesTest.php
index a8107f9..aba2f8f 100644
--- a/tests/Executor/VariablesTest.php
+++ b/tests/Executor/VariablesTest.php
@@ -162,7 +162,8 @@ class VariablesTest extends \PHPUnit_Framework_TestCase
                     'message' =>
                         'Variable "$input" got invalid value {"a":"foo","b":"bar","c":null}.'. "\n".
                         'In field "c": Expected "String!", found null.',
-                    'locations' => [['line' => 2, 'column' => 17]]
+                    'locations' => [['line' => 2, 'column' => 17]],
+                    'category' => 'graphql'
                 ]
             ]
         ];
@@ -178,6 +179,7 @@ class VariablesTest extends \PHPUnit_Framework_TestCase
                         'Variable "$input" got invalid value "foo bar".' . "\n" .
                         'Expected "TestInputObject", found not an object.',
                     'locations' => [ [ 'line' => 2, 'column' => 17 ] ],
+                    'category' => 'graphql',
                 ]
             ]
         ];
@@ -193,7 +195,8 @@ class VariablesTest extends \PHPUnit_Framework_TestCase
                     'message' =>
                         'Variable "$input" got invalid value {"a":"foo","b":"bar"}.'. "\n".
                         'In field "c": Expected "String!", found null.',
-                    'locations' => [['line' => 2, 'column' => 17]]
+                    'locations' => [['line' => 2, 'column' => 17]],
+                    'category' => 'graphql',
                 ]
             ]
         ];
@@ -216,7 +219,8 @@ class VariablesTest extends \PHPUnit_Framework_TestCase
                         'Variable "$input" got invalid value {"na":{"a":"foo"}}.' . "\n" .
                         'In field "na": In field "c": Expected "String!", found null.' . "\n" .
                         'In field "nb": Expected "String!", found null.',
-                    'locations' => [['line' => 2, 'column' => 19]]
+                    'locations' => [['line' => 2, 'column' => 19]],
+                    'category' => 'graphql',
                 ]
             ]
         ];
@@ -232,7 +236,8 @@ class VariablesTest extends \PHPUnit_Framework_TestCase
                     'message' =>
                         'Variable "$input" got invalid value {"a":"foo","b":"bar","c":"baz","d":"dog"}.'."\n".
                         'In field "d": Expected type "ComplexScalar", found "dog".',
-                    'locations' => [['line' => 2, 'column' => 17]]
+                    'locations' => [['line' => 2, 'column' => 17]],
+                    'category' => 'graphql',
                 ]
             ]
         ];
@@ -374,7 +379,8 @@ class VariablesTest extends \PHPUnit_Framework_TestCase
             'errors' => [
                 [
                     'message' => 'Variable "$value" of required type "String!" was not provided.',
-                    'locations' => [['line' => 2, 'column' => 31]]
+                    'locations' => [['line' => 2, 'column' => 31]],
+                    'category' => 'graphql'
                 ]
             ]
         ];
@@ -399,7 +405,8 @@ class VariablesTest extends \PHPUnit_Framework_TestCase
                     'message' =>
                         'Variable "$value" got invalid value null.' . "\n".
                         'Expected "String!", found null.',
-                    'locations' => [['line' => 2, 'column' => 31]]
+                    'locations' => [['line' => 2, 'column' => 31]],
+                    'category' => 'graphql',
                 ]
             ]
         ];
@@ -453,7 +460,8 @@ class VariablesTest extends \PHPUnit_Framework_TestCase
             'errors' => [[
                 'message' => 'Argument "input" of required type "String!" was not provided.',
                 'locations' => [ [ 'line' => 3, 'column' => 9 ] ],
-                'path' => [ 'fieldWithNonNullableStringInput' ]
+                'path' => [ 'fieldWithNonNullableStringInput' ],
+                'category' => 'graphql',
             ]]
         ];
         $this->assertEquals($expected, Executor::execute($this->schema(), $ast)->toArray());
@@ -483,7 +491,8 @@ class VariablesTest extends \PHPUnit_Framework_TestCase
                     'Argument "input" of required type "String!" was provided the ' .
                     'variable "$foo" which was not provided a runtime value.',
                 'locations' => [['line' => 3, 'column' => 48]],
-                'path' => ['fieldWithNonNullableStringInput']
+                'path' => ['fieldWithNonNullableStringInput'],
+                'category' => 'graphql',
             ]]
         ];
         $this->assertEquals($expected, Executor::execute($this->schema(), $ast)->toArray());
@@ -555,7 +564,8 @@ class VariablesTest extends \PHPUnit_Framework_TestCase
                     'message' =>
                         'Variable "$input" got invalid value null.' . "\n" .
                         'Expected "[String]!", found null.',
-                    'locations' => [['line' => 2, 'column' => 17]]
+                    'locations' => [['line' => 2, 'column' => 17]],
+                    'category' => 'graphql',
                 ]
             ]
         ];
@@ -642,7 +652,8 @@ class VariablesTest extends \PHPUnit_Framework_TestCase
                     'message' =>
                         'Variable "$input" got invalid value ["A",null,"B"].' . "\n" .
                         'In element #1: Expected "String!", found null.',
-                    'locations' => [ ['line' => 2, 'column' => 17] ]
+                    'locations' => [ ['line' => 2, 'column' => 17] ],
+                    'category' => 'graphql',
                 ]
             ]
         ];
@@ -667,7 +678,8 @@ class VariablesTest extends \PHPUnit_Framework_TestCase
                     'message' =>
                         'Variable "$input" got invalid value null.' . "\n" .
                         'Expected "[String!]!", found null.',
-                    'locations' => [ ['line' => 2, 'column' => 17] ]
+                    'locations' => [ ['line' => 2, 'column' => 17] ],
+                    'category' => 'graphql',
                 ]
             ]
         ];
@@ -707,7 +719,8 @@ class VariablesTest extends \PHPUnit_Framework_TestCase
                     'message' =>
                         'Variable "$input" got invalid value ["A",null,"B"].'."\n".
                         'In element #1: Expected "String!", found null.',
-                    'locations' => [ ['line' => 2, 'column' => 17] ]
+                    'locations' => [ ['line' => 2, 'column' => 17] ],
+                    'category' => 'graphql',
                 ]
             ]
         ];
@@ -733,7 +746,8 @@ class VariablesTest extends \PHPUnit_Framework_TestCase
                     'message' =>
                         'Variable "$input" expected value of type "TestType!" which cannot ' .
                         'be used as an input type.',
-                    'locations' => [['line' => 2, 'column' => 25]]
+                    'locations' => [['line' => 2, 'column' => 25]],
+                    'category' => 'graphql',
                 ]
             ]
         ];
@@ -760,7 +774,8 @@ class VariablesTest extends \PHPUnit_Framework_TestCase
                     'message' =>
                         'Variable "$input" expected value of type "UnknownType!" which ' .
                         'cannot be used as an input type.',
-                    'locations' => [['line' => 2, 'column' => 25]]
+                    'locations' => [['line' => 2, 'column' => 25]],
+                    'category' => 'graphql',
                 ]
             ]
         ];
@@ -814,7 +829,8 @@ class VariablesTest extends \PHPUnit_Framework_TestCase
                     'Argument "input" got invalid value WRONG_TYPE.' . "\n" .
                     'Expected type "String", found WRONG_TYPE.',
                 'locations' => [ [ 'line' => 2, 'column' => 50 ] ],
-                'path' => [ 'fieldWithDefaultArgumentValue' ]
+                'path' => [ 'fieldWithDefaultArgumentValue' ],
+                'category' => 'graphql',
             ]]
         ];
 
diff --git a/tests/Server/QueryExecutionTest.php b/tests/Server/QueryExecutionTest.php
index 81f1a85..cee3bae 100644
--- a/tests/Server/QueryExecutionTest.php
+++ b/tests/Server/QueryExecutionTest.php
@@ -277,7 +277,8 @@ class QueryExecutionTest extends \PHPUnit_Framework_TestCase
         $expected = [
             'errors' => [
                 [
-                    'message' => 'Persisted queries are not supported by this server'
+                    'message' => 'Persisted queries are not supported by this server',
+                    'category' => 'request'
                 ]
             ]
         ];
@@ -291,7 +292,8 @@ class QueryExecutionTest extends \PHPUnit_Framework_TestCase
         $expected = [
             'errors' => [
                 [
-                    'message' => 'GET supports only query operation'
+                    'message' => 'GET supports only query operation',
+                    'category' => 'request'
                 ]
             ]
         ];
@@ -354,7 +356,8 @@ class QueryExecutionTest extends \PHPUnit_Framework_TestCase
             'errors' => [
                 [
                     'message' => 'Cannot query field "invalid" on type "Query".',
-                    'locations' => [ ['line' => 1, 'column' => 2] ]
+                    'locations' => [ ['line' => 1, 'column' => 2] ],
+                    'category' => 'graphql'
                 ]
             ]
         ];
@@ -391,7 +394,8 @@ class QueryExecutionTest extends \PHPUnit_Framework_TestCase
             'errors' => [
                 [
                     'message' => 'Cannot query field "invalid2" on type "Query".',
-                    'locations' => [ ['line' => 1, 'column' => 2] ]
+                    'locations' => [ ['line' => 1, 'column' => 2] ],
+                    'category' => 'graphql'
                 ]
             ]
         ];
diff --git a/tests/Server/RequestParsingTest.php b/tests/Server/RequestParsingTest.php
index 5f14cc2..8a100f4 100644
--- a/tests/Server/RequestParsingTest.php
+++ b/tests/Server/RequestParsingTest.php
@@ -5,6 +5,7 @@ use GraphQL\Error\Error;
 use GraphQL\Error\InvariantViolation;
 use GraphQL\Server\Helper;
 use GraphQL\Server\OperationParams;
+use GraphQL\Server\RequestError;
 
 class RequestParsingTest extends \PHPUnit_Framework_TestCase
 {
@@ -126,7 +127,7 @@ class RequestParsingTest extends \PHPUnit_Framework_TestCase
     {
         $body = 'not really{} a json';
 
-        $this->setExpectedException(Error::class, 'Could not parse JSON: Syntax error');
+        $this->setExpectedException(RequestError::class, 'Could not parse JSON: Syntax error');
         $this->parseRawRequest('application/json', $body);
     }
 
@@ -134,25 +135,25 @@ class RequestParsingTest extends \PHPUnit_Framework_TestCase
     {
         $body = '"str"';
 
-        $this->setExpectedException(Error::class, 'GraphQL Server expects JSON object or array, but got "str"');
+        $this->setExpectedException(RequestError::class, 'GraphQL Server expects JSON object or array, but got "str"');
         $this->parseRawRequest('application/json', $body);
     }
 
     public function testFailsParsingInvalidContentType()
     {
-        $this->setExpectedException(Error::class, 'Unexpected content type: "not-supported-content-type"');
+        $this->setExpectedException(RequestError::class, 'Unexpected content type: "not-supported-content-type"');
         $this->parseRawRequest('not-supported-content-type', 'test');
     }
 
     public function testFailsWithMissingContentType()
     {
-        $this->setExpectedException(Error::class, 'Missing "Content-Type" header');
+        $this->setExpectedException(RequestError::class, 'Missing "Content-Type" header');
         $this->parseRawRequest(null, 'test');
     }
 
     public function testFailsOnMethodsOtherThanPostOrGet()
     {
-        $this->setExpectedException(Error::class, 'HTTP Method "PUT" is not supported');
+        $this->setExpectedException(RequestError::class, 'HTTP Method "PUT" is not supported');
         $this->parseRawRequest(null, 'test', "PUT");
     }
 
diff --git a/tests/ServerTest.php b/tests/ServerTest.php
index 0ae8eb0..984c858 100644
--- a/tests/ServerTest.php
+++ b/tests/ServerTest.php
@@ -487,10 +487,10 @@ class ServerTest extends \PHPUnit_Framework_TestCase
                 'locations' => [[
                     'line' => 1,
                     'column' => 2
-                ]]
+                ]],
             ]]
         ];
-        $this->assertEquals($expected, $result->toArray());
+        $this->assertArraySubset($expected, $result->toArray());
 
         $server->setDebug(Server::DEBUG_EXCEPTIONS);
         $server->setExceptionFormatter(function($e) {
@@ -507,7 +507,7 @@ class ServerTest extends \PHPUnit_Framework_TestCase
 
         $result = $server->executeQuery('{withException}');
         $expected['errors'][0]['exception'] = ['test' => 'Error'];
-        $this->assertEquals($expected, $result->toArray());
+        $this->assertArraySubset($expected, $result->toArray());
     }
 
     public function testHandleRequest()
@@ -530,7 +530,7 @@ class ServerTest extends \PHPUnit_Framework_TestCase
         $mock->handleRequest();
 
         $this->assertInternalType('array', $output);
-        $this->assertEquals(['errors' => [['message' => 'Unexpected Error']]], $output[0]);
+        $this->assertArraySubset(['errors' => [['message' => 'Unexpected Error']]], $output[0]);
         $this->assertEquals(500, $output[1]);
 
         $output = null;
@@ -565,7 +565,8 @@ class ServerTest extends \PHPUnit_Framework_TestCase
                 'locations' => [[
                     'line' => 1,
                     'column' => 2
-                ]]
+                ]],
+                'category' => 'graphql',
             ]]],
             200
         ];
diff --git a/tests/Type/IntrospectionTest.php b/tests/Type/IntrospectionTest.php
index 8d3f4b9..fcab04d 100644
--- a/tests/Type/IntrospectionTest.php
+++ b/tests/Type/IntrospectionTest.php
@@ -1481,7 +1481,7 @@ class IntrospectionTest extends \PHPUnit_Framework_TestCase
                 )
             ]
         ];
-        $this->assertEquals($expected, GraphQL::execute($schema, $request));
+        $this->assertArraySubset($expected, GraphQL::execute($schema, $request));
     }
 
     /**