diff --git a/src/Language/Visitor.php b/src/Language/Visitor.php
index 8ab3fac..0fecebc 100644
--- a/src/Language/Visitor.php
+++ b/src/Language/Visitor.php
@@ -256,7 +256,9 @@ class Visitor
                                 array_pop($path);
                                 continue;
                             }
-                            $editValue = null;
+                            if ($result->removeNode) {
+                                $editValue = null;
+                            }
                         } else {
                             $editValue = $result;
                         }
@@ -312,7 +314,6 @@ class Visitor
      */
     static function visitInParallel($visitors)
     {
-        // TODO: implement real parallel visiting once PHP supports it
         $visitorsCount = count($visitors);
         $skipping = new \SplFixedArray($visitorsCount);
 
@@ -330,6 +331,8 @@ class Visitor
                                     $skipping[$i] = $node;
                                 } else if ($result->doBreak) {
                                     $skipping[$i] = $result;
+                                } else if ($result->removeNode) {
+                                    return $result;
                                 }
                             } else if ($result !== null) {
                                 return $result;
@@ -348,6 +351,8 @@ class Visitor
                             if ($result instanceof VisitorOperation) {
                                 if ($result->doBreak) {
                                     $skipping[$i] = $result;
+                                } else if ($result->removeNode) {
+                                    return $result;
                                 }
                             } else if ($result !== null) {
                                 return $result;
diff --git a/tests/Language/VisitorTest.php b/tests/Language/VisitorTest.php
index 987e2de..1ad9d59 100644
--- a/tests/Language/VisitorTest.php
+++ b/tests/Language/VisitorTest.php
@@ -8,7 +8,11 @@ use GraphQL\Language\AST\Node;
 use GraphQL\Language\AST\OperationDefinition;
 use GraphQL\Language\AST\SelectionSet;
 use GraphQL\Language\Parser;
+use GraphQL\Language\Printer;
 use GraphQL\Language\Visitor;
+use GraphQL\Tests\Validator\TestCase;
+use GraphQL\Type\Definition\Type;
+use GraphQL\Utils\TypeInfo;
 
 class VisitorTest extends \PHPUnit_Framework_TestCase
 {
@@ -643,4 +647,661 @@ class VisitorTest extends \PHPUnit_Framework_TestCase
 
         $this->assertEquals($expected, $visited);
     }
+
+    // Describe: visitInParallel
+    // Note: nearly identical to the above test of the same test but using visitInParallel.
+
+    /**
+     * @it allows skipping a sub-tree
+     */
+    public function testAllowsSkippingSubTree()
+    {
+        $visited = [];
+
+        $ast = Parser::parse('{ a, b { x }, c }');
+        Visitor::visit($ast, Visitor::visitInParallel([
+            [
+                'enter' => function($node) use (&$visited) {
+                    $visited[] = [ 'enter', $node->kind, isset($node->value) ?  $node->value : null];
+
+                    if ($node->kind === 'Field' && isset($node->name->value) && $node->name->value === 'b') {
+                        return Visitor::skipNode();
+                    }
+                },
+
+                'leave' => function($node) use (&$visited) {
+                    $visited[] = ['leave', $node->kind, isset($node->value) ? $node->value : null];
+                }
+            ]
+        ]));
+
+        $this->assertEquals([
+            [ 'enter', 'Document', null ],
+            [ 'enter', 'OperationDefinition', null ],
+            [ 'enter', 'SelectionSet', null ],
+            [ 'enter', 'Field', null ],
+            [ 'enter', 'Name', 'a' ],
+            [ 'leave', 'Name', 'a' ],
+            [ 'leave', 'Field', null ],
+            [ 'enter', 'Field', null ],
+            [ 'enter', 'Field', null ],
+            [ 'enter', 'Name', 'c' ],
+            [ 'leave', 'Name', 'c' ],
+            [ 'leave', 'Field', null ],
+            [ 'leave', 'SelectionSet', null ],
+            [ 'leave', 'OperationDefinition', null ],
+            [ 'leave', 'Document', null ],
+        ], $visited);
+    }
+
+    /**
+     * @it allows skipping different sub-trees
+     */
+    public function testAllowsSkippingDifferentSubTrees()
+    {
+        $visited = [];
+
+        $ast = Parser::parse('{ a { x }, b { y} }');
+        Visitor::visit($ast, Visitor::visitInParallel([
+        [
+            'enter' => function($node) use (&$visited) {
+                $visited[] = ['no-a', 'enter', $node->kind, isset($node->value) ? $node->value : null];
+                if ($node->kind === 'Field' && isset($node->name->value) && $node->name->value === 'a') {
+                    return Visitor::skipNode();
+                }
+            },
+            'leave' => function($node) use (&$visited) {
+                $visited[] = [ 'no-a', 'leave', $node->kind, isset($node->value) ? $node->value : null ];
+            }
+        ],
+        [
+            'enter' => function($node) use (&$visited) {
+                $visited[] = ['no-b', 'enter', $node->kind, isset($node->value) ? $node->value : null];
+                if ($node->kind === 'Field' && isset($node->name->value) && $node->name->value === 'b') {
+                    return Visitor::skipNode();
+                }
+            },
+            'leave' => function($node) use (&$visited) {
+                $visited[] = ['no-b', 'leave', $node->kind, isset($node->value) ? $node->value : null];
+            }
+        ]
+        ]));
+
+        $this->assertEquals([
+            [ 'no-a', 'enter', 'Document', null ],
+            [ 'no-b', 'enter', 'Document', null ],
+            [ 'no-a', 'enter', 'OperationDefinition', null ],
+            [ 'no-b', 'enter', 'OperationDefinition', null ],
+            [ 'no-a', 'enter', 'SelectionSet', null ],
+            [ 'no-b', 'enter', 'SelectionSet', null ],
+            [ 'no-a', 'enter', 'Field', null ],
+            [ 'no-b', 'enter', 'Field', null ],
+            [ 'no-b', 'enter', 'Name', 'a' ],
+            [ 'no-b', 'leave', 'Name', 'a' ],
+            [ 'no-b', 'enter', 'SelectionSet', null ],
+            [ 'no-b', 'enter', 'Field', null ],
+            [ 'no-b', 'enter', 'Name', 'x' ],
+            [ 'no-b', 'leave', 'Name', 'x' ],
+            [ 'no-b', 'leave', 'Field', null ],
+            [ 'no-b', 'leave', 'SelectionSet', null ],
+            [ 'no-b', 'leave', 'Field', null ],
+            [ 'no-a', 'enter', 'Field', null ],
+            [ 'no-b', 'enter', 'Field', null ],
+            [ 'no-a', 'enter', 'Name', 'b' ],
+            [ 'no-a', 'leave', 'Name', 'b' ],
+            [ 'no-a', 'enter', 'SelectionSet', null ],
+            [ 'no-a', 'enter', 'Field', null ],
+            [ 'no-a', 'enter', 'Name', 'y' ],
+            [ 'no-a', 'leave', 'Name', 'y' ],
+            [ 'no-a', 'leave', 'Field', null ],
+            [ 'no-a', 'leave', 'SelectionSet', null ],
+            [ 'no-a', 'leave', 'Field', null ],
+            [ 'no-a', 'leave', 'SelectionSet', null ],
+            [ 'no-b', 'leave', 'SelectionSet', null ],
+            [ 'no-a', 'leave', 'OperationDefinition', null ],
+            [ 'no-b', 'leave', 'OperationDefinition', null ],
+            [ 'no-a', 'leave', 'Document', null ],
+            [ 'no-b', 'leave', 'Document', null ],
+        ], $visited);
+    }
+
+    /**
+     * @it allows early exit while visiting
+     */
+    public function testAllowsEarlyExitWhileVisiting2()
+    {
+        $visited = [];
+
+        $ast = Parser::parse('{ a, b { x }, c }');
+        Visitor::visit($ast, Visitor::visitInParallel([ [
+            'enter' => function($node) use (&$visited) {
+                $value = isset($node->value) ? $node->value : null;
+                $visited[] = ['enter', $node->kind, $value];
+                if ($node->kind === 'Name' && $value === 'x') {
+                    return Visitor::stop();
+                }
+            },
+            'leave' => function($node) use (&$visited) {
+                $visited[] = ['leave', $node->kind, isset($node->value) ? $node->value : null];
+            }
+        ] ]));
+
+        $this->assertEquals([
+            [ 'enter', 'Document', null ],
+            [ 'enter', 'OperationDefinition', null ],
+            [ 'enter', 'SelectionSet', null ],
+            [ 'enter', 'Field', null ],
+            [ 'enter', 'Name', 'a' ],
+            [ 'leave', 'Name', 'a' ],
+            [ 'leave', 'Field', null ],
+            [ 'enter', 'Field', null ],
+            [ 'enter', 'Name', 'b' ],
+            [ 'leave', 'Name', 'b' ],
+            [ 'enter', 'SelectionSet', null ],
+            [ 'enter', 'Field', null ],
+            [ 'enter', 'Name', 'x' ]
+        ], $visited);
+    }
+
+    /**
+     * @it allows early exit from different points
+     */
+    public function testAllowsEarlyExitFromDifferentPoints()
+    {
+        $visited = [];
+
+        $ast = Parser::parse('{ a { y }, b { x } }');
+        Visitor::visit($ast, Visitor::visitInParallel([
+        [
+            'enter' => function($node) use (&$visited) {
+                $value = isset($node->value) ? $node->value : null;
+                $visited[] = ['break-a', 'enter', $node->kind, $value];
+                if ($node->kind === 'Name' && $value === 'a') {
+                    return Visitor::stop();
+                }
+            },
+            'leave' => function($node) use (&$visited) {
+                $visited[] = [ 'break-a', 'leave', $node->kind, isset($node->value) ? $node->value : null ];
+            }
+        ],
+        [
+            'enter' => function($node) use (&$visited) {
+                $value = isset($node->value) ? $node->value : null;
+                $visited[] = ['break-b', 'enter', $node->kind, $value];
+                if ($node->kind === 'Name' && $value === 'b') {
+                    return Visitor::stop();
+                }
+            },
+            'leave' => function($node) use (&$visited) {
+                $visited[] = ['break-b', 'leave', $node->kind, isset($node->value) ? $node->value : null];
+            }
+        ],
+        ]));
+
+        $this->assertEquals([
+            [ 'break-a', 'enter', 'Document', null ],
+            [ 'break-b', 'enter', 'Document', null ],
+            [ 'break-a', 'enter', 'OperationDefinition', null ],
+            [ 'break-b', 'enter', 'OperationDefinition', null ],
+            [ 'break-a', 'enter', 'SelectionSet', null ],
+            [ 'break-b', 'enter', 'SelectionSet', null ],
+            [ 'break-a', 'enter', 'Field', null ],
+            [ 'break-b', 'enter', 'Field', null ],
+            [ 'break-a', 'enter', 'Name', 'a' ],
+            [ 'break-b', 'enter', 'Name', 'a' ],
+            [ 'break-b', 'leave', 'Name', 'a' ],
+            [ 'break-b', 'enter', 'SelectionSet', null ],
+            [ 'break-b', 'enter', 'Field', null ],
+            [ 'break-b', 'enter', 'Name', 'y' ],
+            [ 'break-b', 'leave', 'Name', 'y' ],
+            [ 'break-b', 'leave', 'Field', null ],
+            [ 'break-b', 'leave', 'SelectionSet', null ],
+            [ 'break-b', 'leave', 'Field', null ],
+            [ 'break-b', 'enter', 'Field', null ],
+            [ 'break-b', 'enter', 'Name', 'b' ]
+        ], $visited);
+    }
+
+    /**
+     * @it allows early exit while leaving
+     */
+    public function testAllowsEarlyExitWhileLeaving2()
+    {
+        $visited = [];
+
+        $ast = Parser::parse('{ a, b { x }, c }');
+        Visitor::visit($ast, Visitor::visitInParallel([ [
+            'enter' => function($node) use (&$visited) {
+                $visited[] = ['enter', $node->kind, isset($node->value) ? $node->value : null];
+            },
+            'leave' => function($node) use (&$visited) {
+                $value = isset($node->value) ? $node->value : null;
+                $visited[] = ['leave', $node->kind, $value];
+                if ($node->kind === 'Name' && $value === 'x') {
+                    return Visitor::stop();
+                }
+            }
+        ] ]));
+
+        $this->assertEquals([
+            [ 'enter', 'Document', null ],
+            [ 'enter', 'OperationDefinition', null ],
+            [ 'enter', 'SelectionSet', null ],
+            [ 'enter', 'Field', null ],
+            [ 'enter', 'Name', 'a' ],
+            [ 'leave', 'Name', 'a' ],
+            [ 'leave', 'Field', null ],
+            [ 'enter', 'Field', null ],
+            [ 'enter', 'Name', 'b' ],
+            [ 'leave', 'Name', 'b' ],
+            [ 'enter', 'SelectionSet', null ],
+            [ 'enter', 'Field', null ],
+            [ 'enter', 'Name', 'x' ],
+            [ 'leave', 'Name', 'x' ]
+        ], $visited);
+    }
+
+    /**
+     * @it allows early exit from leaving different points
+     */
+    public function testAllowsEarlyExitFromLeavingDifferentPoints()
+    {
+        $visited = [];
+
+        $ast = Parser::parse('{ a { y }, b { x } }');
+        Visitor::visit($ast, Visitor::visitInParallel([
+            [
+                'enter' => function($node) use (&$visited) {
+                    $visited[] = ['break-a', 'enter', $node->kind, isset($node->value) ? $node->value : null];
+                },
+                'leave' => function($node) use (&$visited) {
+                    $visited[] = ['break-a', 'leave', $node->kind, isset($node->value) ? $node->value : null];
+                    if ($node->kind === 'Field' && isset($node->name->value) && $node->name->value === 'a') {
+                        return Visitor::stop();
+                    }
+                }
+            ],
+            [
+                'enter' => function($node) use (&$visited) {
+                    $visited[] = ['break-b', 'enter', $node->kind, isset($node->value) ? $node->value : null];
+                },
+                'leave' => function($node) use (&$visited) {
+                    $visited[] = ['break-b', 'leave', $node->kind, isset($node->value) ? $node->value : null];
+                    if ($node->kind === 'Field' && isset($node->name->value) && $node->name->value === 'b') {
+                        return Visitor::stop();
+                    }
+                }
+            ],
+        ]));
+
+        $this->assertEquals([
+            [ 'break-a', 'enter', 'Document', null ],
+            [ 'break-b', 'enter', 'Document', null ],
+            [ 'break-a', 'enter', 'OperationDefinition', null ],
+            [ 'break-b', 'enter', 'OperationDefinition', null ],
+            [ 'break-a', 'enter', 'SelectionSet', null ],
+            [ 'break-b', 'enter', 'SelectionSet', null ],
+            [ 'break-a', 'enter', 'Field', null ],
+            [ 'break-b', 'enter', 'Field', null ],
+            [ 'break-a', 'enter', 'Name', 'a' ],
+            [ 'break-b', 'enter', 'Name', 'a' ],
+            [ 'break-a', 'leave', 'Name', 'a' ],
+            [ 'break-b', 'leave', 'Name', 'a' ],
+            [ 'break-a', 'enter', 'SelectionSet', null ],
+            [ 'break-b', 'enter', 'SelectionSet', null ],
+            [ 'break-a', 'enter', 'Field', null ],
+            [ 'break-b', 'enter', 'Field', null ],
+            [ 'break-a', 'enter', 'Name', 'y' ],
+            [ 'break-b', 'enter', 'Name', 'y' ],
+            [ 'break-a', 'leave', 'Name', 'y' ],
+            [ 'break-b', 'leave', 'Name', 'y' ],
+            [ 'break-a', 'leave', 'Field', null ],
+            [ 'break-b', 'leave', 'Field', null ],
+            [ 'break-a', 'leave', 'SelectionSet', null ],
+            [ 'break-b', 'leave', 'SelectionSet', null ],
+            [ 'break-a', 'leave', 'Field', null ],
+            [ 'break-b', 'leave', 'Field', null ],
+            [ 'break-b', 'enter', 'Field', null ],
+            [ 'break-b', 'enter', 'Name', 'b' ],
+            [ 'break-b', 'leave', 'Name', 'b' ],
+            [ 'break-b', 'enter', 'SelectionSet', null ],
+            [ 'break-b', 'enter', 'Field', null ],
+            [ 'break-b', 'enter', 'Name', 'x' ],
+            [ 'break-b', 'leave', 'Name', 'x' ],
+            [ 'break-b', 'leave', 'Field', null ],
+            [ 'break-b', 'leave', 'SelectionSet', null ],
+            [ 'break-b', 'leave', 'Field', null ]
+        ], $visited);
+    }
+
+    /**
+     * @it allows for editing on enter
+     */
+    public function testAllowsForEditingOnEnter2()
+    {
+        $visited = [];
+
+        $ast = Parser::parse('{ a, b, c { a, b, c } }', ['noLocation' => true]);
+        $editedAst = Visitor::visit($ast, Visitor::visitInParallel([
+            [
+                'enter' => function ($node) use (&$visited) {
+                    if ($node->kind === 'Field' && isset($node->name->value) && $node->name->value === 'b') {
+                        return Visitor::removeNode();
+                    }
+                }
+            ],
+            [
+                'enter' => function ($node) use (&$visited) {
+                    $visited[] = ['enter', $node->kind, isset($node->value) ? $node->value : null];
+                },
+                'leave' => function ($node) use (&$visited) {
+                    $visited[] = ['leave', $node->kind, isset($node->value) ? $node->value : null];
+                }
+            ],
+        ]));
+
+        $this->assertEquals(
+            Parser::parse('{ a, b, c { a, b, c } }', ['noLocation' => true]),
+            $ast
+        );
+
+        $this->assertEquals(
+            Parser::parse('{ a,    c { a,    c } }', ['noLocation' => true]),
+            $editedAst
+        );
+
+        $this->assertEquals([
+            ['enter', 'Document', null],
+            ['enter', 'OperationDefinition', null],
+            ['enter', 'SelectionSet', null],
+            ['enter', 'Field', null],
+            ['enter', 'Name', 'a'],
+            ['leave', 'Name', 'a'],
+            ['leave', 'Field', null],
+            ['enter', 'Field', null],
+            ['enter', 'Name', 'c'],
+            ['leave', 'Name', 'c'],
+            ['enter', 'SelectionSet', null],
+            ['enter', 'Field', null],
+            ['enter', 'Name', 'a'],
+            ['leave', 'Name', 'a'],
+            ['leave', 'Field', null],
+            ['enter', 'Field', null],
+            ['enter', 'Name', 'c'],
+            ['leave', 'Name', 'c'],
+            ['leave', 'Field', null],
+            ['leave', 'SelectionSet', null],
+            ['leave', 'Field', null],
+            ['leave', 'SelectionSet', null],
+            ['leave', 'OperationDefinition', null],
+            ['leave', 'Document', null]
+        ], $visited);
+    }
+
+    /**
+     * @it allows for editing on leave
+     */
+    public function testAllowsForEditingOnLeave2()
+    {
+        $visited = [];
+
+        $ast = Parser::parse('{ a, b, c { a, b, c } }', ['noLocation' => true]);
+        $editedAst = Visitor::visit($ast, Visitor::visitInParallel([
+            [
+                'leave' => function ($node) use (&$visited) {
+                    if ($node->kind === 'Field' && isset($node->name->value) && $node->name->value === 'b') {
+                        return Visitor::removeNode();
+                    }
+                }
+            ],
+            [
+                'enter' => function ($node) use (&$visited) {
+                    $visited[] = ['enter', $node->kind, isset($node->value) ? $node->value : null];
+                },
+                'leave' => function ($node) use (&$visited) {
+                    $visited[] = ['leave', $node->kind, isset($node->value) ? $node->value : null];
+                }
+            ],
+        ]));
+
+        $this->assertEquals(
+            Parser::parse('{ a, b, c { a, b, c } }', ['noLocation' => true]),
+            $ast
+        );
+
+        $this->assertEquals(
+            Parser::parse('{ a,    c { a,    c } }', ['noLocation' => true]),
+            $editedAst
+        );
+
+        $this->assertEquals([
+            ['enter', 'Document', null],
+            ['enter', 'OperationDefinition', null],
+            ['enter', 'SelectionSet', null],
+            ['enter', 'Field', null],
+            ['enter', 'Name', 'a'],
+            ['leave', 'Name', 'a'],
+            ['leave', 'Field', null],
+            ['enter', 'Field', null],
+            ['enter', 'Name', 'b'],
+            ['leave', 'Name', 'b'],
+            ['enter', 'Field', null],
+            ['enter', 'Name', 'c'],
+            ['leave', 'Name', 'c'],
+            ['enter', 'SelectionSet', null],
+            ['enter', 'Field', null],
+            ['enter', 'Name', 'a'],
+            ['leave', 'Name', 'a'],
+            ['leave', 'Field', null],
+            ['enter', 'Field', null],
+            ['enter', 'Name', 'b'],
+            ['leave', 'Name', 'b'],
+            ['enter', 'Field', null],
+            ['enter', 'Name', 'c'],
+            ['leave', 'Name', 'c'],
+            ['leave', 'Field', null],
+            ['leave', 'SelectionSet', null],
+            ['leave', 'Field', null],
+            ['leave', 'SelectionSet', null],
+            ['leave', 'OperationDefinition', null],
+            ['leave', 'Document', null]
+        ], $visited);
+    }
+
+    // Describe: visitWithTypeInfo
+
+    /**
+     * @it maintains type info during visit
+     */
+    public function testMaintainsTypeInfoDuringVisit()
+    {
+        $visited = [];
+
+        $typeInfo = new TypeInfo(TestCase::getDefaultSchema());
+
+        $ast = Parser::parse('{ human(id: 4) { name, pets { name }, unknown } }');
+        Visitor::visit($ast, Visitor::visitWithTypeInfo($typeInfo, [
+            'enter' => function ($node) use ($typeInfo, &$visited) {
+                $parentType = $typeInfo->getParentType();
+                $type = $typeInfo->getType();
+                $inputType = $typeInfo->getInputType();
+                $visited[] = [
+                    'enter',
+                    $node->kind,
+                    $node->kind === 'Name' ? $node->value : null,
+                    $parentType ? (string)$parentType : null,
+                    $type ? (string)$type : null,
+                    $inputType ? (string)$inputType : null
+                ];
+            },
+            'leave' => function ($node) use ($typeInfo, &$visited) {
+                $parentType = $typeInfo->getParentType();
+                $type = $typeInfo->getType();
+                $inputType = $typeInfo->getInputType();
+                $visited[] = [
+                    'leave',
+                    $node->kind,
+                    $node->kind === 'Name' ? $node->value : null,
+                    $parentType ? (string)$parentType : null,
+                    $type ? (string)$type : null,
+                    $inputType ? (string)$inputType : null
+                ];
+            }
+        ]));
+
+        $this->assertEquals([
+            ['enter', 'Document', null, null, null, null],
+            ['enter', 'OperationDefinition', null, null, 'QueryRoot', null],
+            ['enter', 'SelectionSet', null, 'QueryRoot', 'QueryRoot', null],
+            ['enter', 'Field', null, 'QueryRoot', 'Human', null],
+            ['enter', 'Name', 'human', 'QueryRoot', 'Human', null],
+            ['leave', 'Name', 'human', 'QueryRoot', 'Human', null],
+            ['enter', 'Argument', null, 'QueryRoot', 'Human', 'ID'],
+            ['enter', 'Name', 'id', 'QueryRoot', 'Human', 'ID'],
+            ['leave', 'Name', 'id', 'QueryRoot', 'Human', 'ID'],
+            ['enter', 'IntValue', null, 'QueryRoot', 'Human', 'ID'],
+            ['leave', 'IntValue', null, 'QueryRoot', 'Human', 'ID'],
+            ['leave', 'Argument', null, 'QueryRoot', 'Human', 'ID'],
+            ['enter', 'SelectionSet', null, 'Human', 'Human', null],
+            ['enter', 'Field', null, 'Human', 'String', null],
+            ['enter', 'Name', 'name', 'Human', 'String', null],
+            ['leave', 'Name', 'name', 'Human', 'String', null],
+            ['leave', 'Field', null, 'Human', 'String', null],
+            ['enter', 'Field', null, 'Human', '[Pet]', null],
+            ['enter', 'Name', 'pets', 'Human', '[Pet]', null],
+            ['leave', 'Name', 'pets', 'Human', '[Pet]', null],
+            ['enter', 'SelectionSet', null, 'Pet', '[Pet]', null],
+            ['enter', 'Field', null, 'Pet', 'String', null],
+            ['enter', 'Name', 'name', 'Pet', 'String', null],
+            ['leave', 'Name', 'name', 'Pet', 'String', null],
+            ['leave', 'Field', null, 'Pet', 'String', null],
+            ['leave', 'SelectionSet', null, 'Pet', '[Pet]', null],
+            ['leave', 'Field', null, 'Human', '[Pet]', null],
+            ['enter', 'Field', null, 'Human', null, null],
+            ['enter', 'Name', 'unknown', 'Human', null, null],
+            ['leave', 'Name', 'unknown', 'Human', null, null],
+            ['leave', 'Field', null, 'Human', null, null],
+            ['leave', 'SelectionSet', null, 'Human', 'Human', null],
+            ['leave', 'Field', null, 'QueryRoot', 'Human', null],
+            ['leave', 'SelectionSet', null, 'QueryRoot', 'QueryRoot', null],
+            ['leave', 'OperationDefinition', null, null, 'QueryRoot', null],
+            ['leave', 'Document', null, null, null, null]
+        ], $visited);
+    }
+
+    /**
+     * @it maintains type info during edit
+     */
+    public function testMaintainsTypeInfoDuringEdit()
+    {
+        $visited = [];
+        $typeInfo = new TypeInfo(TestCase::getDefaultSchema());
+
+        $ast = Parser::parse(
+            '{ human(id: 4) { name, pets }, alien }'
+        );
+        $editedAst = Visitor::visit($ast, Visitor::visitWithTypeInfo($typeInfo, [
+            'enter' => function ($node) use ($typeInfo, &$visited) {
+                $parentType = $typeInfo->getParentType();
+                $type = $typeInfo->getType();
+                $inputType = $typeInfo->getInputType();
+                $visited[] = [
+                    'enter',
+                    $node->kind,
+                    $node->kind === 'Name' ? $node->value : null,
+                    $parentType ? (string)$parentType : null,
+                    $type ? (string)$type : null,
+                    $inputType ? (string)$inputType : null
+                ];
+
+                // Make a query valid by adding missing selection sets.
+                if (
+                    $node->kind === 'Field' &&
+                    !$node->selectionSet &&
+                    Type::isCompositeType(Type::getNamedType($type))
+                ) {
+                    return new Field([
+                        'alias' => $node->alias,
+                        'name' => $node->name,
+                        'arguments' => $node->arguments,
+                        'directives' => $node->directives,
+                        'selectionSet' => new SelectionSet([
+                            'kind' => 'SelectionSet',
+                            'selections' => [
+                                new Field([
+                                    'name' => new Name(['value' => '__typename'])
+                                ])
+                            ]
+                        ])
+                    ]);
+                }
+            },
+            'leave' => function ($node) use ($typeInfo, &$visited) {
+                $parentType = $typeInfo->getParentType();
+                $type = $typeInfo->getType();
+                $inputType = $typeInfo->getInputType();
+                $visited[] = [
+                    'leave',
+                    $node->kind,
+                    $node->kind === 'Name' ? $node->value : null,
+                    $parentType ? (string)$parentType : null,
+                    $type ? (string)$type : null,
+                    $inputType ? (string)$inputType : null
+                ];
+            }
+        ]));
+
+        $this->assertEquals(Printer::doPrint(Parser::parse(
+            '{ human(id: 4) { name, pets }, alien }'
+        )), Printer::doPrint($ast));
+
+        $this->assertEquals(Printer::doPrint(Parser::parse(
+            '{ human(id: 4) { name, pets { __typename } }, alien { __typename } }'
+        )), Printer::doPrint($editedAst));
+
+        $this->assertEquals([
+            ['enter', 'Document', null, null, null, null],
+            ['enter', 'OperationDefinition', null, null, 'QueryRoot', null],
+            ['enter', 'SelectionSet', null, 'QueryRoot', 'QueryRoot', null],
+            ['enter', 'Field', null, 'QueryRoot', 'Human', null],
+            ['enter', 'Name', 'human', 'QueryRoot', 'Human', null],
+            ['leave', 'Name', 'human', 'QueryRoot', 'Human', null],
+            ['enter', 'Argument', null, 'QueryRoot', 'Human', 'ID'],
+            ['enter', 'Name', 'id', 'QueryRoot', 'Human', 'ID'],
+            ['leave', 'Name', 'id', 'QueryRoot', 'Human', 'ID'],
+            ['enter', 'IntValue', null, 'QueryRoot', 'Human', 'ID'],
+            ['leave', 'IntValue', null, 'QueryRoot', 'Human', 'ID'],
+            ['leave', 'Argument', null, 'QueryRoot', 'Human', 'ID'],
+            ['enter', 'SelectionSet', null, 'Human', 'Human', null],
+            ['enter', 'Field', null, 'Human', 'String', null],
+            ['enter', 'Name', 'name', 'Human', 'String', null],
+            ['leave', 'Name', 'name', 'Human', 'String', null],
+            ['leave', 'Field', null, 'Human', 'String', null],
+            ['enter', 'Field', null, 'Human', '[Pet]', null],
+            ['enter', 'Name', 'pets', 'Human', '[Pet]', null],
+            ['leave', 'Name', 'pets', 'Human', '[Pet]', null],
+            ['enter', 'SelectionSet', null, 'Pet', '[Pet]', null],
+            ['enter', 'Field', null, 'Pet', 'String!', null],
+            ['enter', 'Name', '__typename', 'Pet', 'String!', null],
+            ['leave', 'Name', '__typename', 'Pet', 'String!', null],
+            ['leave', 'Field', null, 'Pet', 'String!', null],
+            ['leave', 'SelectionSet', null, 'Pet', '[Pet]', null],
+            ['leave', 'Field', null, 'Human', '[Pet]', null],
+            ['leave', 'SelectionSet', null, 'Human', 'Human', null],
+            ['leave', 'Field', null, 'QueryRoot', 'Human', null],
+            ['enter', 'Field', null, 'QueryRoot', 'Alien', null],
+            ['enter', 'Name', 'alien', 'QueryRoot', 'Alien', null],
+            ['leave', 'Name', 'alien', 'QueryRoot', 'Alien', null],
+            ['enter', 'SelectionSet', null, 'Alien', 'Alien', null],
+            ['enter', 'Field', null, 'Alien', 'String!', null],
+            ['enter', 'Name', '__typename', 'Alien', 'String!', null],
+            ['leave', 'Name', '__typename', 'Alien', 'String!', null],
+            ['leave', 'Field', null, 'Alien', 'String!', null],
+            ['leave', 'SelectionSet', null, 'Alien', 'Alien', null],
+            ['leave', 'Field', null, 'QueryRoot', 'Alien', null],
+            ['leave', 'SelectionSet', null, 'QueryRoot', 'QueryRoot', null],
+            ['leave', 'OperationDefinition', null, null, 'QueryRoot', null],
+            ['leave', 'Document', null, null, null, null]
+        ], $visited);
+    }
 }
diff --git a/tests/Validator/TestCase.php b/tests/Validator/TestCase.php
index ed77714..23f921b 100644
--- a/tests/Validator/TestCase.php
+++ b/tests/Validator/TestCase.php
@@ -15,12 +15,10 @@ use GraphQL\Validator\DocumentValidator;
 
 abstract class TestCase extends \PHPUnit_Framework_TestCase
 {
-    public $humanType;
-
     /**
      * @return Schema
      */
-    protected function getDefaultSchema()
+    public static function getDefaultSchema()
     {
         $FurColor = null;
 
@@ -124,7 +122,8 @@ abstract class TestCase extends \PHPUnit_Framework_TestCase
             ]
         ]);
 
-        $Human = $this->humanType = new ObjectType([
+        $Human = null;
+        $Human = new ObjectType([
             'name' => 'Human',
             'isTypeOf' => function() {return true;},
             'interfaces' => [$Being, $Intelligent],
@@ -134,7 +133,7 @@ abstract class TestCase extends \PHPUnit_Framework_TestCase
                     'args' => ['surname' => ['type' => Type::boolean()]]
                 ],
                 'pets' => ['type' => Type::listOf($Pet)],
-                'relatives' => ['type' => function() {return Type::listOf($this->humanType); }],
+                'relatives' => ['type' => function() use (&$Human) {return Type::listOf($Human); }],
                 'iq' => ['type' => Type::int()]
             ]
         ]);