diff --git a/tests/Error/ErrorTest.php b/tests/Error/ErrorTest.php
index 03abbad..3ea9974 100644
--- a/tests/Error/ErrorTest.php
+++ b/tests/Error/ErrorTest.php
@@ -1,4 +1,7 @@
 <?php
+
+declare(strict_types=1);
+
 namespace GraphQL\Tests\Error;
 
 use GraphQL\Error\Error;
@@ -10,27 +13,27 @@ use PHPUnit\Framework\TestCase;
 class ErrorTest extends TestCase
 {
     /**
-     * @it uses the stack of an original error
+     * @see it('uses the stack of an original error')
      */
-    public function testUsesTheStackOfAnOriginalError()
+    public function testUsesTheStackOfAnOriginalError() : void
     {
-        $prev = new \Exception("Original");
-        $err = new Error('msg', null, null, null, null, $prev);
+        $prev = new \Exception('Original');
+        $err  = new Error('msg', null, null, null, null, $prev);
 
         $this->assertSame($err->getPrevious(), $prev);
     }
 
     /**
-     * @it converts nodes to positions and locations
+     * @see it('converts nodes to positions and locations')
      */
-    public function testConvertsNodesToPositionsAndLocations()
+    public function testConvertsNodesToPositionsAndLocations() : void
     {
-        $source = new Source('{
+        $source    = new Source('{
       field
     }');
-        $ast = Parser::parse($source);
+        $ast       = Parser::parse($source);
         $fieldNode = $ast->definitions[0]->selectionSet->selections[0];
-        $e = new Error('msg', [ $fieldNode ]);
+        $e         = new Error('msg', [$fieldNode]);
 
         $this->assertEquals([$fieldNode], $e->nodes);
         $this->assertEquals($source, $e->getSource());
@@ -39,16 +42,16 @@ class ErrorTest extends TestCase
     }
 
     /**
-     * @it converts single node to positions and locations
+     * @see it('converts single node to positions and locations')
      */
-    public function testConvertSingleNodeToPositionsAndLocations()
+    public function testConvertSingleNodeToPositionsAndLocations() : void
     {
-        $source = new Source('{
+        $source    = new Source('{
       field
     }');
-        $ast = Parser::parse($source);
+        $ast       = Parser::parse($source);
         $fieldNode = $ast->definitions[0]->selectionSet->selections[0];
-        $e = new Error('msg', $fieldNode); // Non-array value.
+        $e         = new Error('msg', $fieldNode); // Non-array value.
 
         $this->assertEquals([$fieldNode], $e->nodes);
         $this->assertEquals($source, $e->getSource());
@@ -57,16 +60,16 @@ class ErrorTest extends TestCase
     }
 
     /**
-     * @it converts node with loc.start === 0 to positions and locations
+     * @see it('converts node with loc.start === 0 to positions and locations')
      */
-    public function testConvertsNodeWithStart0ToPositionsAndLocations()
+    public function testConvertsNodeWithStart0ToPositionsAndLocations() : void
     {
-        $source = new Source('{
+        $source        = new Source('{
       field
     }');
-        $ast = Parser::parse($source);
+        $ast           = Parser::parse($source);
         $operationNode = $ast->definitions[0];
-        $e = new Error('msg', [ $operationNode ]);
+        $e             = new Error('msg', [$operationNode]);
 
         $this->assertEquals([$operationNode], $e->nodes);
         $this->assertEquals($source, $e->getSource());
@@ -75,14 +78,14 @@ class ErrorTest extends TestCase
     }
 
     /**
-     * @it converts source and positions to locations
+     * @see it('converts source and positions to locations')
      */
-    public function testConvertsSourceAndPositionsToLocations()
+    public function testConvertsSourceAndPositionsToLocations() : void
     {
         $source = new Source('{
       field
     }');
-        $e = new Error('msg', null, $source, [ 10 ]);
+        $e      = new Error('msg', null, $source, [10]);
 
         $this->assertEquals(null, $e->nodes);
         $this->assertEquals($source, $e->getSource());
@@ -91,21 +94,21 @@ class ErrorTest extends TestCase
     }
 
     /**
-     * @it serializes to include message
+     * @see it('serializes to include message')
      */
-    public function testSerializesToIncludeMessage()
+    public function testSerializesToIncludeMessage() : void
     {
         $e = new Error('msg');
         $this->assertEquals(['message' => 'msg'], $e->toSerializableArray());
     }
 
     /**
-     * @it serializes to include message and locations
+     * @see it('serializes to include message and locations')
      */
-    public function testSerializesToIncludeMessageAndLocations()
+    public function testSerializesToIncludeMessageAndLocations() : void
     {
         $node = Parser::parse('{ field }')->definitions[0]->selectionSet->selections[0];
-        $e = new Error('msg', [ $node ]);
+        $e    = new Error('msg', [$node]);
 
         $this->assertEquals(
             ['message' => 'msg', 'locations' => [['line' => 1, 'column' => 3]]],
@@ -114,26 +117,26 @@ class ErrorTest extends TestCase
     }
 
     /**
-     * @it serializes to include path
+     * @see it('serializes to include path')
      */
-    public function testSerializesToIncludePath()
+    public function testSerializesToIncludePath() : void
     {
         $e = new Error(
             'msg',
             null,
             null,
             null,
-            [ 'path', 3, 'to', 'field' ]
+            ['path', 3, 'to', 'field']
         );
 
-        $this->assertEquals([ 'path', 3, 'to', 'field' ], $e->path);
-        $this->assertEquals(['message' => 'msg', 'path' => [ 'path', 3, 'to', 'field' ]], $e->toSerializableArray());
+        $this->assertEquals(['path', 3, 'to', 'field'], $e->path);
+        $this->assertEquals(['message' => 'msg', 'path' => ['path', 3, 'to', 'field']], $e->toSerializableArray());
     }
 
     /**
-     * @it default error formatter includes extension fields
+     * @see it('default error formatter includes extension fields')
      */
-    public function testDefaultErrorFormatterIncludesExtensionFields()
+    public function testDefaultErrorFormatterIncludesExtensionFields() : void
     {
         $e = new Error(
             'msg',
@@ -146,9 +149,12 @@ class ErrorTest extends TestCase
         );
 
         $this->assertEquals(['foo' => 'bar'], $e->getExtensions());
-        $this->assertEquals([
-            'message' => 'msg',
-            'extensions' => ['foo' => 'bar'],
-        ], $e->toSerializableArray());
+        $this->assertEquals(
+            [
+                'message'    => 'msg',
+                'extensions' => ['foo' => 'bar'],
+            ],
+            $e->toSerializableArray()
+        );
     }
 }
diff --git a/tests/Error/PrintErrorTest.php b/tests/Error/PrintErrorTest.php
index 8cff56c..86c9c55 100644
--- a/tests/Error/PrintErrorTest.php
+++ b/tests/Error/PrintErrorTest.php
@@ -1,4 +1,7 @@
 <?php
+
+declare(strict_types=1);
+
 namespace GraphQL\Tests\Error;
 
 use GraphQL\Error\Error;
@@ -10,12 +13,10 @@ use PHPUnit\Framework\TestCase;
 
 class PrintErrorTest extends TestCase
 {
-    // Describe printError
-
     /**
-     * @it prints an line numbers with correct padding
+     * @see it('prints an line numbers with correct padding')
      */
-    public function testPrintsAnLineNumbersWithCorrectPadding()
+    public function testPrintsAnLineNumbersWithCorrectPadding() : void
     {
         $singleDigit = new Error(
             'Single digit line number with no padding',
@@ -24,7 +25,7 @@ class PrintErrorTest extends TestCase
             [0]
         );
 
-        $actual = FormattedError::printError($singleDigit);
+        $actual   = FormattedError::printError($singleDigit);
         $expected = 'Single digit line number with no padding
 
 Test (9:1)
@@ -39,8 +40,8 @@ Test (9:1)
             new Source("*\n", 'Test', new SourceLocation(9, 1)),
             [0]
         );
-        $actual = FormattedError::printError($doubleDigit);
-        $expected = 'Left padded first line number
+        $actual      = FormattedError::printError($doubleDigit);
+        $expected    = 'Left padded first line number
 
 Test (9:1)
  9: *
@@ -51,19 +52,21 @@ Test (9:1)
     }
 
     /**
-     * @it prints an error with nodes from different sources
+     * @see it('prints an error with nodes from different sources')
      */
-    public function testPrintsAnErrorWithNodesFromDifferentSources()
+    public function testPrintsAnErrorWithNodesFromDifferentSources() : void
     {
-        $sourceA = Parser::parse(new Source('type Foo {
+        $sourceA = Parser::parse(new Source(
+            'type Foo {
   field: String
 }',
-        'SourceA'
+            'SourceA'
         ));
 
         $fieldTypeA = $sourceA->definitions[0]->fields[0]->type;
 
-        $sourceB = Parser::parse(new Source('type Foo {
+        $sourceB = Parser::parse(new Source(
+            'type Foo {
   field: Int
 }',
             'SourceB'
@@ -71,7 +74,6 @@ Test (9:1)
 
         $fieldTypeB = $sourceB->definitions[0]->fields[0]->type;
 
-
         $error = new Error(
             'Example error with two nodes',
             [