diff --git a/test/PhpParser/Builder/ClassConstTest.php b/test/PhpParser/Builder/ClassConstTest.php
index 4a71e0fdd5..f0cccfd2c8 100644
--- a/test/PhpParser/Builder/ClassConstTest.php
+++ b/test/PhpParser/Builder/ClassConstTest.php
@@ -20,7 +20,7 @@ public function createClassConstBuilder($name, $value) {
         return new ClassConst($name, $value);
     }
 
-    public function testModifiers() {
+    public function testModifiers(): void {
         $node = $this->createClassConstBuilder("TEST", 1)
             ->makePrivate()
             ->getNode()
@@ -82,7 +82,7 @@ public function testModifiers() {
         );
     }
 
-    public function testDocComment() {
+    public function testDocComment(): void {
         $node = $this->createClassConstBuilder('TEST', 1)
             ->setDocComment('/** Test */')
             ->makePublic()
@@ -102,7 +102,7 @@ public function testDocComment() {
         );
     }
 
-    public function testAddConst() {
+    public function testAddConst(): void {
         $node = $this->createClassConstBuilder('FIRST_TEST', 1)
             ->addConst("SECOND_TEST", 2)
             ->getNode();
@@ -118,7 +118,7 @@ public function testAddConst() {
         );
     }
 
-    public function testAddAttribute() {
+    public function testAddAttribute(): void {
         $attribute = new Attribute(
             new Name('Attr'),
             [new Arg(new Int_(1), false, false, [], new Identifier('name'))]
@@ -142,7 +142,7 @@ public function testAddAttribute() {
         );
     }
 
-    public function testType() {
+    public function testType(): void {
         $node = $this->createClassConstBuilder('TYPE', 1)
             ->setType('int')
             ->getNode();
@@ -157,7 +157,7 @@ public function testType() {
     /**
      * @dataProvider provideTestDefaultValues
      */
-    public function testValues($value, $expectedValueNode) {
+    public function testValues($value, $expectedValueNode): void {
         $node = $this->createClassConstBuilder('TEST', $value)
             ->getNode()
         ;
diff --git a/test/PhpParser/Builder/ClassTest.php b/test/PhpParser/Builder/ClassTest.php
index 334a85382c..69866b7b79 100644
--- a/test/PhpParser/Builder/ClassTest.php
+++ b/test/PhpParser/Builder/ClassTest.php
@@ -18,7 +18,7 @@ protected function createClassBuilder($class) {
         return new Class_($class);
     }
 
-    public function testExtendsImplements() {
+    public function testExtendsImplements(): void {
         $node = $this->createClassBuilder('SomeLogger')
             ->extend('BaseLogger')
             ->implement('Namespaced\Logger', new Name('SomeInterface'))
@@ -40,7 +40,7 @@ public function testExtendsImplements() {
         );
     }
 
-    public function testAbstract() {
+    public function testAbstract(): void {
         $node = $this->createClassBuilder('Test')
             ->makeAbstract()
             ->getNode()
@@ -54,7 +54,7 @@ public function testAbstract() {
         );
     }
 
-    public function testFinal() {
+    public function testFinal(): void {
         $node = $this->createClassBuilder('Test')
             ->makeFinal()
             ->getNode()
@@ -68,7 +68,7 @@ public function testFinal() {
         );
     }
 
-    public function testReadonly() {
+    public function testReadonly(): void {
         $node = $this->createClassBuilder('Test')
             ->makeReadonly()
             ->getNode()
@@ -82,7 +82,7 @@ public function testReadonly() {
         );
     }
 
-    public function testStatementOrder() {
+    public function testStatementOrder(): void {
         $method = new Stmt\ClassMethod('testMethod');
         $property = new Stmt\Property(
             Modifiers::PUBLIC,
@@ -108,7 +108,7 @@ public function testStatementOrder() {
         );
     }
 
-    public function testDocComment() {
+    public function testDocComment(): void {
         $docComment = <<<'DOC'
 /**
  * Test
@@ -141,7 +141,7 @@ public function testDocComment() {
         );
     }
 
-    public function testAddAttribute() {
+    public function testAddAttribute(): void {
         $attribute = new Attribute(
             new Name('Attr'),
             [new Arg(new Int_(1), false, false, [], new Identifier('name'))]
@@ -162,7 +162,7 @@ public function testAddAttribute() {
         );
     }
 
-    public function testInvalidStmtError() {
+    public function testInvalidStmtError(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Unexpected node of type "Stmt_Echo"');
         $this->createClassBuilder('Test')
@@ -170,21 +170,21 @@ public function testInvalidStmtError() {
         ;
     }
 
-    public function testInvalidDocComment() {
+    public function testInvalidDocComment(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Doc comment must be a string or an instance of PhpParser\Comment\Doc');
         $this->createClassBuilder('Test')
             ->setDocComment(new Comment('Test'));
     }
 
-    public function testEmptyName() {
+    public function testEmptyName(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Name cannot be empty');
         $this->createClassBuilder('Test')
             ->extend('');
     }
 
-    public function testInvalidName() {
+    public function testInvalidName(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Name must be a string or an instance of Node\Name');
         $this->createClassBuilder('Test')
diff --git a/test/PhpParser/Builder/EnumCaseTest.php b/test/PhpParser/Builder/EnumCaseTest.php
index 66eb10c3dd..fb0ddfafab 100644
--- a/test/PhpParser/Builder/EnumCaseTest.php
+++ b/test/PhpParser/Builder/EnumCaseTest.php
@@ -17,7 +17,7 @@ public function createEnumCaseBuilder($name) {
         return new EnumCase($name);
     }
 
-    public function testDocComment() {
+    public function testDocComment(): void {
         $node = $this->createEnumCaseBuilder('TEST')
             ->setDocComment('/** Test */')
             ->getNode();
@@ -35,7 +35,7 @@ public function testDocComment() {
         );
     }
 
-    public function testAddAttribute() {
+    public function testAddAttribute(): void {
         $attribute = new Attribute(
             new Name('Attr'),
             [new Arg(new Int_(1), false, false, [], new Identifier('name'))]
@@ -59,7 +59,7 @@ public function testAddAttribute() {
     /**
      * @dataProvider provideTestDefaultValues
      */
-    public function testValues($value, $expectedValueNode) {
+    public function testValues($value, $expectedValueNode): void {
         $node = $this->createEnumCaseBuilder('TEST')
             ->setValue($value)
             ->getNode()
diff --git a/test/PhpParser/Builder/EnumTest.php b/test/PhpParser/Builder/EnumTest.php
index c88a8d6069..f62392a26c 100644
--- a/test/PhpParser/Builder/EnumTest.php
+++ b/test/PhpParser/Builder/EnumTest.php
@@ -17,7 +17,7 @@ protected function createEnumBuilder($class) {
         return new Enum_($class);
     }
 
-    public function testImplements() {
+    public function testImplements(): void {
         $node = $this->createEnumBuilder('SomeEnum')
             ->implement('Namespaced\SomeInterface', new Name('OtherInterface'))
             ->getNode()
@@ -34,7 +34,7 @@ public function testImplements() {
         );
     }
 
-    public function testSetScalarType() {
+    public function testSetScalarType(): void {
         $node = $this->createEnumBuilder('Test')
             ->setScalarType('int')
             ->getNode()
@@ -48,7 +48,7 @@ public function testSetScalarType() {
         );
     }
 
-    public function testStatementOrder() {
+    public function testStatementOrder(): void {
         $method = new Stmt\ClassMethod('testMethod');
         $enumCase = new Stmt\EnumCase(
             'TEST_ENUM_CASE'
@@ -73,7 +73,7 @@ public function testStatementOrder() {
         );
     }
 
-    public function testDocComment() {
+    public function testDocComment(): void {
         $docComment = <<<'DOC'
 /**
  * Test
@@ -106,7 +106,7 @@ public function testDocComment() {
         );
     }
 
-    public function testAddAttribute() {
+    public function testAddAttribute(): void {
         $attribute = new Attribute(
             new Name('Attr'),
             [new Arg(new Int_(1), false, false, [], new Identifier('name'))]
@@ -127,7 +127,7 @@ public function testAddAttribute() {
         );
     }
 
-    public function testInvalidStmtError() {
+    public function testInvalidStmtError(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Unexpected node of type "PropertyItem"');
         $this->createEnumBuilder('Test')
@@ -135,21 +135,21 @@ public function testInvalidStmtError() {
         ;
     }
 
-    public function testInvalidDocComment() {
+    public function testInvalidDocComment(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Doc comment must be a string or an instance of PhpParser\Comment\Doc');
         $this->createEnumBuilder('Test')
             ->setDocComment(new Comment('Test'));
     }
 
-    public function testEmptyName() {
+    public function testEmptyName(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Name cannot be empty');
         $this->createEnumBuilder('Test')
             ->implement('');
     }
 
-    public function testInvalidName() {
+    public function testInvalidName(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Name must be a string or an instance of Node\Name');
         $this->createEnumBuilder('Test')
diff --git a/test/PhpParser/Builder/FunctionTest.php b/test/PhpParser/Builder/FunctionTest.php
index 2fdecf7f6f..1b60112731 100644
--- a/test/PhpParser/Builder/FunctionTest.php
+++ b/test/PhpParser/Builder/FunctionTest.php
@@ -20,7 +20,7 @@ public function createFunctionBuilder($name) {
         return new Function_($name);
     }
 
-    public function testReturnByRef() {
+    public function testReturnByRef(): void {
         $node = $this->createFunctionBuilder('test')
             ->makeReturnByRef()
             ->getNode()
@@ -34,7 +34,7 @@ public function testReturnByRef() {
         );
     }
 
-    public function testParams() {
+    public function testParams(): void {
         $param1 = new Node\Param(new Variable('test1'));
         $param2 = new Node\Param(new Variable('test2'));
         $param3 = new Node\Param(new Variable('test3'));
@@ -53,7 +53,7 @@ public function testParams() {
         );
     }
 
-    public function testStmts() {
+    public function testStmts(): void {
         $stmt1 = new Print_(new String_('test1'));
         $stmt2 = new Print_(new String_('test2'));
         $stmt3 = new Print_(new String_('test3'));
@@ -76,7 +76,7 @@ public function testStmts() {
         );
     }
 
-    public function testDocComment() {
+    public function testDocComment(): void {
         $node = $this->createFunctionBuilder('test')
             ->setDocComment('/** Test */')
             ->getNode();
@@ -86,7 +86,7 @@ public function testDocComment() {
         ]), $node);
     }
 
-    public function testAddAttribute() {
+    public function testAddAttribute(): void {
         $attribute = new Attribute(
             new Name('Attr'),
             [new Arg(new Int_(1), false, false, [], new Identifier('name'))]
@@ -102,7 +102,7 @@ public function testAddAttribute() {
         ], []), $node);
     }
 
-    public function testReturnType() {
+    public function testReturnType(): void {
         $node = $this->createFunctionBuilder('test')
             ->setReturnType('void')
             ->getNode();
@@ -112,13 +112,13 @@ public function testReturnType() {
         ], []), $node);
     }
 
-    public function testInvalidNullableVoidType() {
+    public function testInvalidNullableVoidType(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('void type cannot be nullable');
         $this->createFunctionBuilder('test')->setReturnType('?void');
     }
 
-    public function testInvalidParamError() {
+    public function testInvalidParamError(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Expected parameter node, got "Name"');
         $this->createFunctionBuilder('test')
@@ -126,7 +126,7 @@ public function testInvalidParamError() {
         ;
     }
 
-    public function testAddNonStmt() {
+    public function testAddNonStmt(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Expected statement or expression node');
         $this->createFunctionBuilder('test')
diff --git a/test/PhpParser/Builder/InterfaceTest.php b/test/PhpParser/Builder/InterfaceTest.php
index 71652f72c1..75f2ed7d27 100644
--- a/test/PhpParser/Builder/InterfaceTest.php
+++ b/test/PhpParser/Builder/InterfaceTest.php
@@ -23,13 +23,13 @@ private function dump($node) {
         return $pp->prettyPrint([$node]);
     }
 
-    public function testEmpty() {
+    public function testEmpty(): void {
         $contract = $this->createInterfaceBuilder()->getNode();
         $this->assertInstanceOf(Stmt\Interface_::class, $contract);
         $this->assertEquals(new Node\Identifier('Contract'), $contract->name);
     }
 
-    public function testExtending() {
+    public function testExtending(): void {
         $contract = $this->createInterfaceBuilder()
             ->extend('Space\Root1', 'Root2')->getNode();
         $this->assertEquals(
@@ -42,13 +42,13 @@ public function testExtending() {
         );
     }
 
-    public function testAddMethod() {
+    public function testAddMethod(): void {
         $method = new Stmt\ClassMethod('doSomething');
         $contract = $this->createInterfaceBuilder()->addStmt($method)->getNode();
         $this->assertSame([$method], $contract->stmts);
     }
 
-    public function testAddConst() {
+    public function testAddConst(): void {
         $const = new Stmt\ClassConst([
             new Node\Const_('SPEED_OF_LIGHT', new Float_(299792458.0))
         ]);
@@ -56,7 +56,7 @@ public function testAddConst() {
         $this->assertSame(299792458.0, $contract->stmts[0]->consts[0]->value->value);
     }
 
-    public function testOrder() {
+    public function testOrder(): void {
         $const = new Stmt\ClassConst([
             new Node\Const_('SPEED_OF_LIGHT', new Float_(299792458))
         ]);
@@ -71,7 +71,7 @@ public function testOrder() {
         $this->assertInstanceOf(Stmt\ClassMethod::class, $contract->stmts[1]);
     }
 
-    public function testDocComment() {
+    public function testDocComment(): void {
         $node = $this->createInterfaceBuilder()
             ->setDocComment('/** Test */')
             ->getNode();
@@ -81,7 +81,7 @@ public function testDocComment() {
         ]), $node);
     }
 
-    public function testAddAttribute() {
+    public function testAddAttribute(): void {
         $attribute = new Attribute(
             new Name('Attr'),
             [new Arg(new Int_(1), false, false, [], new Identifier('name'))]
@@ -97,13 +97,13 @@ public function testAddAttribute() {
         ], []), $node);
     }
 
-    public function testInvalidStmtError() {
+    public function testInvalidStmtError(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Unexpected node of type "PropertyItem"');
         $this->createInterfaceBuilder()->addStmt(new Node\PropertyItem('invalid'));
     }
 
-    public function testFullFunctional() {
+    public function testFullFunctional(): void {
         $const = new Stmt\ClassConst([
             new Node\Const_('SPEED_OF_LIGHT', new Float_(299792458))
         ]);
diff --git a/test/PhpParser/Builder/MethodTest.php b/test/PhpParser/Builder/MethodTest.php
index 807072d735..a5ff8f7c80 100644
--- a/test/PhpParser/Builder/MethodTest.php
+++ b/test/PhpParser/Builder/MethodTest.php
@@ -21,7 +21,7 @@ public function createMethodBuilder($name) {
         return new Method($name);
     }
 
-    public function testModifiers() {
+    public function testModifiers(): void {
         $node = $this->createMethodBuilder('test')
             ->makePublic()
             ->makeAbstract()
@@ -63,7 +63,7 @@ public function testModifiers() {
         );
     }
 
-    public function testReturnByRef() {
+    public function testReturnByRef(): void {
         $node = $this->createMethodBuilder('test')
             ->makeReturnByRef()
             ->getNode()
@@ -77,7 +77,7 @@ public function testReturnByRef() {
         );
     }
 
-    public function testParams() {
+    public function testParams(): void {
         $param1 = new Node\Param(new Variable('test1'));
         $param2 = new Node\Param(new Variable('test2'));
         $param3 = new Node\Param(new Variable('test3'));
@@ -96,7 +96,7 @@ public function testParams() {
         );
     }
 
-    public function testStmts() {
+    public function testStmts(): void {
         $stmt1 = new Print_(new String_('test1'));
         $stmt2 = new Print_(new String_('test2'));
         $stmt3 = new Print_(new String_('test3'));
@@ -118,7 +118,7 @@ public function testStmts() {
             $node
         );
     }
-    public function testDocComment() {
+    public function testDocComment(): void {
         $node = $this->createMethodBuilder('test')
             ->setDocComment('/** Test */')
             ->getNode();
@@ -128,7 +128,7 @@ public function testDocComment() {
         ]), $node);
     }
 
-    public function testAddAttribute() {
+    public function testAddAttribute(): void {
         $attribute = new Attribute(
             new Name('Attr'),
             [new Arg(new Int_(1), false, false, [], new Identifier('name'))]
@@ -144,7 +144,7 @@ public function testAddAttribute() {
         ], []), $node);
     }
 
-    public function testReturnType() {
+    public function testReturnType(): void {
         $node = $this->createMethodBuilder('test')
             ->setReturnType('bool')
             ->getNode();
@@ -153,7 +153,7 @@ public function testReturnType() {
         ], []), $node);
     }
 
-    public function testAddStmtToAbstractMethodError() {
+    public function testAddStmtToAbstractMethodError(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Cannot add statements to an abstract method');
         $this->createMethodBuilder('test')
@@ -162,7 +162,7 @@ public function testAddStmtToAbstractMethodError() {
         ;
     }
 
-    public function testMakeMethodWithStmtsAbstractError() {
+    public function testMakeMethodWithStmtsAbstractError(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Cannot make method with statements abstract');
         $this->createMethodBuilder('test')
@@ -171,7 +171,7 @@ public function testMakeMethodWithStmtsAbstractError() {
         ;
     }
 
-    public function testInvalidParamError() {
+    public function testInvalidParamError(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Expected parameter node, got "Name"');
         $this->createMethodBuilder('test')
diff --git a/test/PhpParser/Builder/NamespaceTest.php b/test/PhpParser/Builder/NamespaceTest.php
index 10a3870a83..2cce107f47 100644
--- a/test/PhpParser/Builder/NamespaceTest.php
+++ b/test/PhpParser/Builder/NamespaceTest.php
@@ -11,7 +11,7 @@ protected function createNamespaceBuilder($fqn) {
         return new Namespace_($fqn);
     }
 
-    public function testCreation() {
+    public function testCreation(): void {
         $stmt1 = new Stmt\Class_('SomeClass');
         $stmt2 = new Stmt\Interface_('SomeInterface');
         $stmt3 = new Stmt\Function_('someFunction');
diff --git a/test/PhpParser/Builder/ParamTest.php b/test/PhpParser/Builder/ParamTest.php
index 58a6c04287..f1ac65bb8a 100644
--- a/test/PhpParser/Builder/ParamTest.php
+++ b/test/PhpParser/Builder/ParamTest.php
@@ -21,7 +21,7 @@ public function createParamBuilder($name) {
     /**
      * @dataProvider provideTestDefaultValues
      */
-    public function testDefaultValues($value, $expectedValueNode) {
+    public function testDefaultValues($value, $expectedValueNode): void {
         $node = $this->createParamBuilder('test')
             ->setDefault($value)
             ->getNode()
@@ -89,7 +89,7 @@ public function provideTestDefaultValues() {
      * @dataProvider provideTestNullableTypes
      * @dataProvider provideTestUnionTypes
      */
-    public function testTypes($typeHint, $expectedType) {
+    public function testTypes($typeHint, $expectedType): void {
         $node = $this->createParamBuilder('test')
             ->setType($typeHint)
             ->getNode()
@@ -169,19 +169,19 @@ public function provideTestUnionTypes() {
         ];
     }
 
-    public function testVoidTypeError() {
+    public function testVoidTypeError(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Parameter type cannot be void');
         $this->createParamBuilder('test')->setType('void');
     }
 
-    public function testInvalidTypeError() {
+    public function testInvalidTypeError(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Type must be a string, or an instance of Name, Identifier or ComplexType');
         $this->createParamBuilder('test')->setType(new \stdClass());
     }
 
-    public function testByRef() {
+    public function testByRef(): void {
         $node = $this->createParamBuilder('test')
             ->makeByRef()
             ->getNode()
@@ -193,7 +193,7 @@ public function testByRef() {
         );
     }
 
-    public function testVariadic() {
+    public function testVariadic(): void {
         $node = $this->createParamBuilder('test')
             ->makeVariadic()
             ->getNode()
@@ -205,7 +205,7 @@ public function testVariadic() {
         );
     }
 
-    public function testMakePublic() {
+    public function testMakePublic(): void {
         $node = $this->createParamBuilder('test')
             ->makePublic()
             ->getNode()
@@ -217,7 +217,7 @@ public function testMakePublic() {
         );
     }
 
-    public function testMakeProtected() {
+    public function testMakeProtected(): void {
         $node = $this->createParamBuilder('test')
             ->makeProtected()
             ->getNode()
@@ -229,7 +229,7 @@ public function testMakeProtected() {
         );
     }
 
-    public function testMakePrivate() {
+    public function testMakePrivate(): void {
         $node = $this->createParamBuilder('test')
             ->makePrivate()
             ->getNode()
@@ -241,7 +241,7 @@ public function testMakePrivate() {
         );
     }
 
-    public function testMakeReadonly() {
+    public function testMakeReadonly(): void {
         $node = $this->createParamBuilder('test')
             ->makeReadonly()
             ->getNode()
@@ -253,7 +253,7 @@ public function testMakeReadonly() {
         );
     }
 
-    public function testAddAttribute() {
+    public function testAddAttribute(): void {
         $attribute = new Attribute(
             new Name('Attr'),
             [new Arg(new Int_(1), false, false, [], new Identifier('name'))]
diff --git a/test/PhpParser/Builder/PropertyTest.php b/test/PhpParser/Builder/PropertyTest.php
index 50fff0a8ac..b2983141cf 100644
--- a/test/PhpParser/Builder/PropertyTest.php
+++ b/test/PhpParser/Builder/PropertyTest.php
@@ -19,7 +19,7 @@ public function createPropertyBuilder($name) {
         return new Property($name);
     }
 
-    public function testModifiers() {
+    public function testModifiers(): void {
         $node = $this->createPropertyBuilder('test')
             ->makePrivate()
             ->makeStatic()
@@ -82,7 +82,7 @@ public function testModifiers() {
         );
     }
 
-    public function testDocComment() {
+    public function testDocComment(): void {
         $node = $this->createPropertyBuilder('test')
             ->setDocComment('/** Test */')
             ->getNode();
@@ -101,7 +101,7 @@ public function testDocComment() {
     /**
      * @dataProvider provideTestDefaultValues
      */
-    public function testDefaultValues($value, $expectedValueNode) {
+    public function testDefaultValues($value, $expectedValueNode): void {
         $node = $this->createPropertyBuilder('test')
             ->setDefault($value)
             ->getNode()
@@ -110,7 +110,7 @@ public function testDefaultValues($value, $expectedValueNode) {
         $this->assertEquals($expectedValueNode, $node->props[0]->default);
     }
 
-    public function testAddAttribute() {
+    public function testAddAttribute(): void {
         $attribute = new Attribute(
             new Name('Attr'),
             [new Arg(new Int_(1), false, false, [], new Identifier('name'))]
diff --git a/test/PhpParser/Builder/TraitTest.php b/test/PhpParser/Builder/TraitTest.php
index 850f198bbe..ddb9f9d631 100644
--- a/test/PhpParser/Builder/TraitTest.php
+++ b/test/PhpParser/Builder/TraitTest.php
@@ -23,7 +23,7 @@ protected function createTraitBuilder($class) {
         return new Trait_($class);
     }
 
-    public function testStmtAddition() {
+    public function testStmtAddition(): void {
         $method1 = new Stmt\ClassMethod('test1');
         $method2 = new Stmt\ClassMethod('test2');
         $method3 = new Stmt\ClassMethod('test3');
@@ -49,7 +49,7 @@ public function testStmtAddition() {
         ]), $trait);
     }
 
-    public function testInvalidStmtError() {
+    public function testInvalidStmtError(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Unexpected node of type "Stmt_Echo"');
         $this->createTraitBuilder('Test')
@@ -57,7 +57,7 @@ public function testInvalidStmtError() {
         ;
     }
 
-    public function testGetMethods() {
+    public function testGetMethods(): void {
         $methods = [
             new ClassMethod('foo'),
             new ClassMethod('bar'),
@@ -77,7 +77,7 @@ public function testGetMethods() {
         $this->assertSame($methods, $trait->getMethods());
     }
 
-    public function testGetProperties() {
+    public function testGetProperties(): void {
         $properties = [
             new Property(Modifiers::PUBLIC, [new PropertyItem('foo')]),
             new Property(Modifiers::PUBLIC, [new PropertyItem('bar')]),
@@ -95,7 +95,7 @@ public function testGetProperties() {
         $this->assertSame($properties, $trait->getProperties());
     }
 
-    public function testAddAttribute() {
+    public function testAddAttribute(): void {
         $attribute = new Attribute(
             new Name('Attr'),
             [new Arg(new Int_(1), false, false, [], new Identifier('name'))]
diff --git a/test/PhpParser/Builder/TraitUseAdaptationTest.php b/test/PhpParser/Builder/TraitUseAdaptationTest.php
index d08850bd1f..56ab75f185 100644
--- a/test/PhpParser/Builder/TraitUseAdaptationTest.php
+++ b/test/PhpParser/Builder/TraitUseAdaptationTest.php
@@ -12,7 +12,7 @@ protected function createTraitUseAdaptationBuilder($trait, $method) {
         return new TraitUseAdaptation($trait, $method);
     }
 
-    public function testAsMake() {
+    public function testAsMake(): void {
         $builder = $this->createTraitUseAdaptationBuilder(null, 'foo');
 
         $this->assertEquals(
@@ -36,7 +36,7 @@ public function testAsMake() {
         );
     }
 
-    public function testInsteadof() {
+    public function testInsteadof(): void {
         $node = $this->createTraitUseAdaptationBuilder('SomeTrait', 'foo')
             ->insteadof('AnotherTrait')
             ->getNode()
@@ -52,7 +52,7 @@ public function testInsteadof() {
         );
     }
 
-    public function testAsOnNotAlias() {
+    public function testAsOnNotAlias(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Cannot set alias for not alias adaptation buider');
         $this->createTraitUseAdaptationBuilder('Test', 'foo')
@@ -61,7 +61,7 @@ public function testAsOnNotAlias() {
         ;
     }
 
-    public function testInsteadofOnNotPrecedence() {
+    public function testInsteadofOnNotPrecedence(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Cannot add overwritten traits for not precedence adaptation buider');
         $this->createTraitUseAdaptationBuilder('Test', 'foo')
@@ -70,7 +70,7 @@ public function testInsteadofOnNotPrecedence() {
         ;
     }
 
-    public function testInsteadofWithoutTrait() {
+    public function testInsteadofWithoutTrait(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Precedence adaptation must have trait');
         $this->createTraitUseAdaptationBuilder(null, 'foo')
@@ -78,7 +78,7 @@ public function testInsteadofWithoutTrait() {
         ;
     }
 
-    public function testMakeOnNotAlias() {
+    public function testMakeOnNotAlias(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Cannot set access modifier for not alias adaptation buider');
         $this->createTraitUseAdaptationBuilder('Test', 'foo')
@@ -87,7 +87,7 @@ public function testMakeOnNotAlias() {
         ;
     }
 
-    public function testMultipleMake() {
+    public function testMultipleMake(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Multiple access type modifiers are not allowed');
         $this->createTraitUseAdaptationBuilder(null, 'foo')
@@ -96,7 +96,7 @@ public function testMultipleMake() {
         ;
     }
 
-    public function testUndefinedType() {
+    public function testUndefinedType(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Type of adaptation is not defined');
         $this->createTraitUseAdaptationBuilder(null, 'foo')
diff --git a/test/PhpParser/Builder/TraitUseTest.php b/test/PhpParser/Builder/TraitUseTest.php
index b7bb527302..8101b777cb 100644
--- a/test/PhpParser/Builder/TraitUseTest.php
+++ b/test/PhpParser/Builder/TraitUseTest.php
@@ -10,7 +10,7 @@ protected function createTraitUseBuilder(...$traits) {
         return new TraitUse(...$traits);
     }
 
-    public function testAnd() {
+    public function testAnd(): void {
         $node = $this->createTraitUseBuilder('SomeTrait')
             ->and('AnotherTrait')
             ->getNode()
@@ -25,7 +25,7 @@ public function testAnd() {
         );
     }
 
-    public function testWith() {
+    public function testWith(): void {
         $node = $this->createTraitUseBuilder('SomeTrait')
             ->with(new Stmt\TraitUseAdaptation\Alias(null, 'foo', null, 'bar'))
             ->with((new TraitUseAdaptation(null, 'test'))->as('baz'))
@@ -41,7 +41,7 @@ public function testWith() {
         );
     }
 
-    public function testInvalidAdaptationNode() {
+    public function testInvalidAdaptationNode(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Adaptation must have type TraitUseAdaptation');
         $this->createTraitUseBuilder('Test')
diff --git a/test/PhpParser/Builder/UseTest.php b/test/PhpParser/Builder/UseTest.php
index 2952d44099..5e5601589b 100644
--- a/test/PhpParser/Builder/UseTest.php
+++ b/test/PhpParser/Builder/UseTest.php
@@ -11,7 +11,7 @@ protected function createUseBuilder($name, $type = Stmt\Use_::TYPE_NORMAL) {
         return new Builder\Use_($name, $type);
     }
 
-    public function testCreation() {
+    public function testCreation(): void {
         $node = $this->createUseBuilder('Foo\Bar')->getNode();
         $this->assertEquals(new Stmt\Use_([
             new \PhpParser\Node\UseItem(new Name('Foo\Bar'), null)
diff --git a/test/PhpParser/BuilderFactoryTest.php b/test/PhpParser/BuilderFactoryTest.php
index a86e17e14f..8c08cc205e 100644
--- a/test/PhpParser/BuilderFactoryTest.php
+++ b/test/PhpParser/BuilderFactoryTest.php
@@ -15,7 +15,7 @@ class BuilderFactoryTest extends \PHPUnit\Framework\TestCase {
     /**
      * @dataProvider provideTestFactory
      */
-    public function testFactory($methodName, $className) {
+    public function testFactory($methodName, $className): void {
         $factory = new BuilderFactory();
         $this->assertInstanceOf($className, $factory->$methodName('test'));
     }
@@ -38,12 +38,12 @@ public function provideTestFactory() {
         ];
     }
 
-    public function testFactoryClassConst() {
+    public function testFactoryClassConst(): void {
         $factory = new BuilderFactory();
         $this->assertInstanceOf(Builder\ClassConst::class, $factory->classConst('TEST', 1));
     }
 
-    public function testAttribute() {
+    public function testAttribute(): void {
         $factory = new BuilderFactory();
         $this->assertEquals(
             new Attribute(new Name('AttributeName'), [new Arg(
@@ -53,7 +53,7 @@ public function testAttribute() {
         );
     }
 
-    public function testVal() {
+    public function testVal(): void {
         // This method is a wrapper around BuilderHelpers::normalizeValue(),
         // which is already tested elsewhere
         $factory = new BuilderFactory();
@@ -63,7 +63,7 @@ public function testVal() {
         );
     }
 
-    public function testConcat() {
+    public function testConcat(): void {
         $factory = new BuilderFactory();
         $varA = new Expr\Variable('a');
         $varB = new Expr\Variable('b');
@@ -83,19 +83,19 @@ public function testConcat() {
         );
     }
 
-    public function testConcatOneError() {
+    public function testConcatOneError(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Expected at least two expressions');
         (new BuilderFactory())->concat("a");
     }
 
-    public function testConcatInvalidExpr() {
+    public function testConcatInvalidExpr(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Expected string or Expr');
         (new BuilderFactory())->concat("a", 42);
     }
 
-    public function testArgs() {
+    public function testArgs(): void {
         $factory = new BuilderFactory();
         $unpack = new Arg(new Expr\Variable('c'), false, true);
         $this->assertEquals(
@@ -108,7 +108,7 @@ public function testArgs() {
         );
     }
 
-    public function testNamedArgs() {
+    public function testNamedArgs(): void {
         $factory = new BuilderFactory();
         $this->assertEquals(
             [
@@ -119,7 +119,7 @@ public function testNamedArgs() {
         );
     }
 
-    public function testCalls() {
+    public function testCalls(): void {
         $factory = new BuilderFactory();
 
         // Simple function call
@@ -195,7 +195,7 @@ public function testCalls() {
         );
     }
 
-    public function testConstFetches() {
+    public function testConstFetches(): void {
         $factory = new BuilderFactory();
         $this->assertEquals(
             new Expr\ConstFetch(new Name('FOO')),
@@ -215,7 +215,7 @@ public function testConstFetches() {
         );
     }
 
-    public function testVar() {
+    public function testVar(): void {
         $factory = new BuilderFactory();
         $this->assertEquals(
             new Expr\Variable("foo"),
@@ -227,7 +227,7 @@ public function testVar() {
         );
     }
 
-    public function testPropertyFetch() {
+    public function testPropertyFetch(): void {
         $f = new BuilderFactory();
         $this->assertEquals(
             new Expr\PropertyFetch(new Expr\Variable('foo'), 'bar'),
@@ -243,31 +243,31 @@ public function testPropertyFetch() {
         );
     }
 
-    public function testInvalidIdentifier() {
+    public function testInvalidIdentifier(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Expected string or instance of Node\Identifier');
         (new BuilderFactory())->classConstFetch('Foo', new Name('foo'));
     }
 
-    public function testInvalidIdentifierOrExpr() {
+    public function testInvalidIdentifierOrExpr(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Expected string or instance of Node\Identifier or Node\Expr');
         (new BuilderFactory())->staticCall('Foo', new Name('bar'));
     }
 
-    public function testInvalidNameOrExpr() {
+    public function testInvalidNameOrExpr(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Name must be a string or an instance of Node\Name or Node\Expr');
         (new BuilderFactory())->funcCall(new Node\Stmt\Return_());
     }
 
-    public function testInvalidVar() {
+    public function testInvalidVar(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Variable name must be string or Expr');
         (new BuilderFactory())->var(new Node\Stmt\Return_());
     }
 
-    public function testIntegration() {
+    public function testIntegration(): void {
         $factory = new BuilderFactory();
         $node = $factory->namespace('Name\Space')
             ->addStmt($factory->use('Foo\Bar\SomeOtherClass'))
diff --git a/test/PhpParser/BuilderHelpersTest.php b/test/PhpParser/BuilderHelpersTest.php
index d70be9d8ce..0e89e47fbb 100644
--- a/test/PhpParser/BuilderHelpersTest.php
+++ b/test/PhpParser/BuilderHelpersTest.php
@@ -9,7 +9,7 @@
 use PhpParser\Node\Expr;
 
 class BuilderHelpersTest extends \PHPUnit\Framework\TestCase {
-    public function testNormalizeNode() {
+    public function testNormalizeNode(): void {
         $builder = new Class_('SomeClass');
         $this->assertEquals($builder->getNode(), BuilderHelpers::normalizeNode($builder));
 
@@ -21,7 +21,7 @@ public function testNormalizeNode() {
         BuilderHelpers::normalizeNode('test');
     }
 
-    public function testNormalizeStmt() {
+    public function testNormalizeStmt(): void {
         $stmt = new Node\Stmt\Class_('Class');
         $this->assertSame($stmt, BuilderHelpers::normalizeStmt($stmt));
 
@@ -35,13 +35,13 @@ public function testNormalizeStmt() {
         BuilderHelpers::normalizeStmt(new Node\Attribute(new Node\Name('Test')));
     }
 
-    public function testNormalizeStmtInvalidType() {
+    public function testNormalizeStmtInvalidType(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Expected node or builder object');
         BuilderHelpers::normalizeStmt('test');
     }
 
-    public function testNormalizeIdentifier() {
+    public function testNormalizeIdentifier(): void {
         $identifier = new Node\Identifier('fn');
         $this->assertSame($identifier, BuilderHelpers::normalizeIdentifier($identifier));
         $this->assertEquals($identifier, BuilderHelpers::normalizeIdentifier('fn'));
@@ -51,7 +51,7 @@ public function testNormalizeIdentifier() {
         BuilderHelpers::normalizeIdentifier(1);
     }
 
-    public function testNormalizeIdentifierOrExpr() {
+    public function testNormalizeIdentifierOrExpr(): void {
         $identifier = new Node\Identifier('fn');
         $this->assertSame($identifier, BuilderHelpers::normalizeIdentifierOrExpr($identifier));
 
@@ -64,7 +64,7 @@ public function testNormalizeIdentifierOrExpr() {
         BuilderHelpers::normalizeIdentifierOrExpr(1);
     }
 
-    public function testNormalizeName() {
+    public function testNormalizeName(): void {
         $name = new Node\Name('test');
         $this->assertSame($name, BuilderHelpers::normalizeName($name));
         $this->assertEquals(
@@ -82,13 +82,13 @@ public function testNormalizeName() {
         BuilderHelpers::normalizeName('');
     }
 
-    public function testNormalizeNameInvalidType() {
+    public function testNormalizeNameInvalidType(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Name must be a string or an instance of Node\Name');
         BuilderHelpers::normalizeName(1);
     }
 
-    public function testNormalizeNameOrExpr() {
+    public function testNormalizeNameOrExpr(): void {
         $expr = new Expr\Variable('fn');
         $this->assertSame($expr, BuilderHelpers::normalizeNameOrExpr($expr));
 
@@ -109,13 +109,13 @@ public function testNormalizeNameOrExpr() {
         BuilderHelpers::normalizeNameOrExpr('');
     }
 
-    public function testNormalizeNameOrExpInvalidType() {
+    public function testNormalizeNameOrExpInvalidType(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Name must be a string or an instance of Node\Name or Node\Expr');
         BuilderHelpers::normalizeNameOrExpr(1);
     }
 
-    public function testNormalizeType() {
+    public function testNormalizeType(): void {
         $this->assertEquals(new Node\Identifier('array'), BuilderHelpers::normalizeType('array'));
         $this->assertEquals(new Node\Identifier('callable'), BuilderHelpers::normalizeType('callable'));
         $this->assertEquals(new Node\Identifier('string'), BuilderHelpers::normalizeType('string'));
@@ -156,25 +156,25 @@ public function testNormalizeType() {
         BuilderHelpers::normalizeType(1);
     }
 
-    public function testNormalizeTypeNullableVoid() {
+    public function testNormalizeTypeNullableVoid(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('void type cannot be nullable');
         BuilderHelpers::normalizeType('?void');
     }
 
-    public function testNormalizeTypeNullableMixed() {
+    public function testNormalizeTypeNullableMixed(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('mixed type cannot be nullable');
         BuilderHelpers::normalizeType('?mixed');
     }
 
-    public function testNormalizeTypeNullableNever() {
+    public function testNormalizeTypeNullableNever(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('never type cannot be nullable');
         BuilderHelpers::normalizeType('?never');
     }
 
-    public function testNormalizeValue() {
+    public function testNormalizeValue(): void {
         $expression = new Scalar\Int_(1);
         $this->assertSame($expression, BuilderHelpers::normalizeValue($expression));
 
@@ -200,7 +200,7 @@ public function testNormalizeValue() {
         BuilderHelpers::normalizeValue(new \stdClass());
     }
 
-    public function testNormalizeDocComment() {
+    public function testNormalizeDocComment(): void {
         $docComment = new Comment\Doc('Some doc comment');
         $this->assertSame($docComment, BuilderHelpers::normalizeDocComment($docComment));
 
@@ -211,7 +211,7 @@ public function testNormalizeDocComment() {
         BuilderHelpers::normalizeDocComment(1);
     }
 
-    public function testNormalizeAttribute() {
+    public function testNormalizeAttribute(): void {
         $attribute = new Node\Attribute(new Node\Name('Test'));
         $attributeGroup = new Node\AttributeGroup([$attribute]);
 
diff --git a/test/PhpParser/CodeParsingTest.php b/test/PhpParser/CodeParsingTest.php
index d4da650a26..b843e2860a 100644
--- a/test/PhpParser/CodeParsingTest.php
+++ b/test/PhpParser/CodeParsingTest.php
@@ -9,7 +9,7 @@ class CodeParsingTest extends CodeTestAbstract {
     /**
      * @dataProvider provideTestParse
      */
-    public function testParse($name, $code, $expected, $modeLine) {
+    public function testParse($name, $code, $expected, $modeLine): void {
         $modes = $this->parseModeLine($modeLine);
         $parser = $this->createParser($modes['version'] ?? null);
         list($stmts, $output) = $this->getParseOutput($parser, $code, $modes);
@@ -62,13 +62,13 @@ private function formatErrorMessage(Error $e, $code) {
         return $e->getMessage();
     }
 
-    private function checkAttributes($stmts) {
+    private function checkAttributes($stmts): void {
         if ($stmts === null) {
             return;
         }
 
         $traverser = new NodeTraverser(new class () extends NodeVisitorAbstract {
-            public function enterNode(Node $node) {
+            public function enterNode(Node $node): void {
                 $startLine = $node->getStartLine();
                 $endLine = $node->getEndLine();
                 $startFilePos = $node->getStartFilePos();
diff --git a/test/PhpParser/CommentTest.php b/test/PhpParser/CommentTest.php
index c97308d9f1..255eccb801 100644
--- a/test/PhpParser/CommentTest.php
+++ b/test/PhpParser/CommentTest.php
@@ -3,7 +3,7 @@
 namespace PhpParser;
 
 class CommentTest extends \PHPUnit\Framework\TestCase {
-    public function testGetters() {
+    public function testGetters(): void {
         $comment = new Comment('/* Some comment */',
             1, 10, 2, 1, 27, 2);
 
@@ -20,7 +20,7 @@ public function testGetters() {
     /**
      * @dataProvider provideTestReformatting
      */
-    public function testReformatting($commentText, $reformattedText) {
+    public function testReformatting($commentText, $reformattedText): void {
         $comment = new Comment($commentText);
         $this->assertSame($reformattedText, $comment->getReformattedText());
     }
diff --git a/test/PhpParser/CompatibilityTest.php b/test/PhpParser/CompatibilityTest.php
index 71f1f236b8..9928e8d85f 100644
--- a/test/PhpParser/CompatibilityTest.php
+++ b/test/PhpParser/CompatibilityTest.php
@@ -13,7 +13,7 @@ class CompatibilityTest extends \PHPUnit\Framework\TestCase {
      * @runInSeparateProcess
      * @preserveGlobalState disabled
      */
-    public function testAliases1() {
+    public function testAliases1(): void {
         $var = new Expr\Variable('x');
         $node = new Node\ClosureUse($var);
         $this->assertTrue($node instanceof Expr\ClosureUse);
@@ -41,7 +41,7 @@ public function testAliases1() {
      * @runInSeparateProcess
      * @preserveGlobalState disabled
      */
-    public function testAliases2() {
+    public function testAliases2(): void {
         $var = new Expr\Variable('x');
         $node = new Node\Expr\ClosureUse($var);
         $this->assertTrue($node instanceof Node\ClosureUse);
diff --git a/test/PhpParser/ConstExprEvaluatorTest.php b/test/PhpParser/ConstExprEvaluatorTest.php
index 9d78af88a9..0f5ac79420 100644
--- a/test/PhpParser/ConstExprEvaluatorTest.php
+++ b/test/PhpParser/ConstExprEvaluatorTest.php
@@ -7,7 +7,7 @@
 
 class ConstExprEvaluatorTest extends \PHPUnit\Framework\TestCase {
     /** @dataProvider provideTestEvaluate */
-    public function testEvaluate($exprString, $expected) {
+    public function testEvaluate($exprString, $expected): void {
         $parser = new Parser\Php7(new Lexer());
         $expr = $parser->parse('<?php ' . $exprString . ';')[0]->expr;
         $evaluator = new ConstExprEvaluator();
@@ -74,14 +74,14 @@ public function provideTestEvaluate() {
         ];
     }
 
-    public function testEvaluateFails() {
+    public function testEvaluateFails(): void {
         $this->expectException(ConstExprEvaluationException::class);
         $this->expectExceptionMessage('Expression of type Expr_Variable cannot be evaluated');
         $evaluator = new ConstExprEvaluator();
         $evaluator->evaluateDirectly(new Expr\Variable('a'));
     }
 
-    public function testEvaluateFallback() {
+    public function testEvaluateFallback(): void {
         $evaluator = new ConstExprEvaluator(function (Expr $expr) {
             if ($expr instanceof Scalar\MagicConst\Line) {
                 return 42;
@@ -98,7 +98,7 @@ public function testEvaluateFallback() {
     /**
      * @dataProvider provideTestEvaluateSilently
      */
-    public function testEvaluateSilently($expr, $exception, $msg) {
+    public function testEvaluateSilently($expr, $exception, $msg): void {
         $evaluator = new ConstExprEvaluator();
 
         try {
diff --git a/test/PhpParser/ErrorHandler/CollectingTest.php b/test/PhpParser/ErrorHandler/CollectingTest.php
index 83b1cbd0ac..631b0b0ba4 100644
--- a/test/PhpParser/ErrorHandler/CollectingTest.php
+++ b/test/PhpParser/ErrorHandler/CollectingTest.php
@@ -5,7 +5,7 @@
 use PhpParser\Error;
 
 class CollectingTest extends \PHPUnit\Framework\TestCase {
-    public function testHandleError() {
+    public function testHandleError(): void {
         $errorHandler = new Collecting();
         $this->assertFalse($errorHandler->hasErrors());
         $this->assertEmpty($errorHandler->getErrors());
diff --git a/test/PhpParser/ErrorHandler/ThrowingTest.php b/test/PhpParser/ErrorHandler/ThrowingTest.php
index 61efd7bcfd..8442600a63 100644
--- a/test/PhpParser/ErrorHandler/ThrowingTest.php
+++ b/test/PhpParser/ErrorHandler/ThrowingTest.php
@@ -5,7 +5,7 @@
 use PhpParser\Error;
 
 class ThrowingTest extends \PHPUnit\Framework\TestCase {
-    public function testHandleError() {
+    public function testHandleError(): void {
         $this->expectException(Error::class);
         $this->expectExceptionMessage('Test');
         $errorHandler = new Throwing();
diff --git a/test/PhpParser/ErrorTest.php b/test/PhpParser/ErrorTest.php
index f378ab234d..b3ef521e67 100644
--- a/test/PhpParser/ErrorTest.php
+++ b/test/PhpParser/ErrorTest.php
@@ -22,7 +22,7 @@ public function testConstruct() {
     /**
      * @depends testConstruct
      */
-    public function testSetMessageAndLine(Error $error) {
+    public function testSetMessageAndLine(Error $error): void {
         $error->setRawMessage('Some other error');
         $this->assertSame('Some other error', $error->getRawMessage());
 
@@ -31,7 +31,7 @@ public function testSetMessageAndLine(Error $error) {
         $this->assertSame('Some other error on line 15', $error->getMessage());
     }
 
-    public function testUnknownLine() {
+    public function testUnknownLine(): void {
         $error = new Error('Some error');
 
         $this->assertSame(-1, $error->getStartLine());
@@ -40,7 +40,7 @@ public function testUnknownLine() {
     }
 
     /** @dataProvider provideTestColumnInfo */
-    public function testColumnInfo($code, $startPos, $endPos, $startColumn, $endColumn) {
+    public function testColumnInfo($code, $startPos, $endPos, $startColumn, $endColumn): void {
         $error = new Error('Some error', [
             'startFilePos' => $startPos,
             'endFilePos' => $endPos,
@@ -72,7 +72,7 @@ public function provideTestColumnInfo() {
         ];
     }
 
-    public function testNoColumnInfo() {
+    public function testNoColumnInfo(): void {
         $error = new Error('Some error', ['startLine' => 3]);
 
         $this->assertFalse($error->hasColumnInfo());
@@ -90,7 +90,7 @@ public function testNoColumnInfo() {
         }
     }
 
-    public function testInvalidPosInfo() {
+    public function testInvalidPosInfo(): void {
         $this->expectException(\RuntimeException::class);
         $this->expectExceptionMessage('Invalid position information');
         $error = new Error('Some error', [
diff --git a/test/PhpParser/Internal/DifferTest.php b/test/PhpParser/Internal/DifferTest.php
index 8b84c1a0d5..039335eee4 100644
--- a/test/PhpParser/Internal/DifferTest.php
+++ b/test/PhpParser/Internal/DifferTest.php
@@ -28,7 +28,7 @@ private function formatDiffString(array $diff) {
     }
 
     /** @dataProvider provideTestDiff */
-    public function testDiff($oldStr, $newStr, $expectedDiffStr) {
+    public function testDiff($oldStr, $newStr, $expectedDiffStr): void {
         $differ = new Differ(function ($a, $b) {
             return $a === $b;
         });
@@ -49,7 +49,7 @@ public function provideTestDiff() {
     }
 
     /** @dataProvider provideTestDiffWithReplacements */
-    public function testDiffWithReplacements($oldStr, $newStr, $expectedDiffStr) {
+    public function testDiffWithReplacements($oldStr, $newStr, $expectedDiffStr): void {
         $differ = new Differ(function ($a, $b) {
             return $a === $b;
         });
@@ -66,7 +66,7 @@ public function provideTestDiffWithReplacements() {
         ];
     }
 
-    public function testNonContiguousIndices() {
+    public function testNonContiguousIndices(): void {
         $differ = new Differ(function ($a, $b) {
             return $a === $b;
         });
diff --git a/test/PhpParser/JsonDecoderTest.php b/test/PhpParser/JsonDecoderTest.php
index 28fa4ed28b..3fb105f96d 100644
--- a/test/PhpParser/JsonDecoderTest.php
+++ b/test/PhpParser/JsonDecoderTest.php
@@ -3,7 +3,7 @@
 namespace PhpParser;
 
 class JsonDecoderTest extends \PHPUnit\Framework\TestCase {
-    public function testRoundTrip() {
+    public function testRoundTrip(): void {
         $code = <<<'PHP'
 <?php
 // comment
@@ -23,7 +23,7 @@ function functionName(&$a = 0, $b = 1.0) {
     }
 
     /** @dataProvider provideTestDecodingError */
-    public function testDecodingError($json, $expectedMessage) {
+    public function testDecodingError($json, $expectedMessage): void {
         $jsonDecoder = new JsonDecoder();
         $this->expectException(\RuntimeException::class);
         $this->expectExceptionMessage($expectedMessage);
diff --git a/test/PhpParser/Lexer/EmulativeTest.php b/test/PhpParser/Lexer/EmulativeTest.php
index 46ea65e449..f77da514be 100644
--- a/test/PhpParser/Lexer/EmulativeTest.php
+++ b/test/PhpParser/Lexer/EmulativeTest.php
@@ -19,7 +19,7 @@ protected function getLexer() {
     /**
      * @dataProvider provideTestReplaceKeywords
      */
-    public function testReplaceKeywords(string $keyword, int $expectedToken) {
+    public function testReplaceKeywords(string $keyword, int $expectedToken): void {
         $lexer = $this->getLexer();
         $code = '<?php ' . $keyword;
         $this->assertEquals([
@@ -32,7 +32,7 @@ public function testReplaceKeywords(string $keyword, int $expectedToken) {
     /**
      * @dataProvider provideTestReplaceKeywords
      */
-    public function testReplaceKeywordsUppercase(string $keyword, int $expectedToken) {
+    public function testReplaceKeywordsUppercase(string $keyword, int $expectedToken): void {
         $lexer = $this->getLexer();
         $code = '<?php ' . strtoupper($keyword);
 
@@ -46,7 +46,7 @@ public function testReplaceKeywordsUppercase(string $keyword, int $expectedToken
     /**
      * @dataProvider provideTestReplaceKeywords
      */
-    public function testNoReplaceKeywordsAfterObjectOperator(string $keyword) {
+    public function testNoReplaceKeywordsAfterObjectOperator(string $keyword): void {
         $lexer = $this->getLexer();
         $code = '<?php ->' . $keyword;
 
@@ -61,7 +61,7 @@ public function testNoReplaceKeywordsAfterObjectOperator(string $keyword) {
     /**
      * @dataProvider provideTestReplaceKeywords
      */
-    public function testNoReplaceKeywordsAfterObjectOperatorWithSpaces(string $keyword) {
+    public function testNoReplaceKeywordsAfterObjectOperatorWithSpaces(string $keyword): void {
         $lexer = $this->getLexer();
         $code = '<?php ->    ' . $keyword;
 
@@ -77,7 +77,7 @@ public function testNoReplaceKeywordsAfterObjectOperatorWithSpaces(string $keywo
     /**
      * @dataProvider provideTestReplaceKeywords
      */
-    public function testNoReplaceKeywordsAfterNullsafeObjectOperator(string $keyword) {
+    public function testNoReplaceKeywordsAfterNullsafeObjectOperator(string $keyword): void {
         $lexer = $this->getLexer();
         $code = '<?php ?->' . $keyword;
 
@@ -115,7 +115,7 @@ public function provideTestReplaceKeywords() {
         ];
     }
 
-    private function assertSameTokens(array $expectedTokens, array $tokens) {
+    private function assertSameTokens(array $expectedTokens, array $tokens): void {
         $reducedTokens = [];
         foreach ($tokens as $token) {
             if ($token->id === 0 || $token->isIgnorable()) {
@@ -129,7 +129,7 @@ private function assertSameTokens(array $expectedTokens, array $tokens) {
     /**
      * @dataProvider provideTestLexNewFeatures
      */
-    public function testLexNewFeatures(string $code, array $expectedTokens) {
+    public function testLexNewFeatures(string $code, array $expectedTokens): void {
         $lexer = $this->getLexer();
         $this->assertSameTokens($expectedTokens, $lexer->tokenize('<?php ' . $code));
     }
@@ -137,7 +137,7 @@ public function testLexNewFeatures(string $code, array $expectedTokens) {
     /**
      * @dataProvider provideTestLexNewFeatures
      */
-    public function testLeaveStuffAloneInStrings(string $code) {
+    public function testLeaveStuffAloneInStrings(string $code): void {
         $stringifiedToken = '"' . addcslashes($code, '"\\') . '"';
 
         $lexer = $this->getLexer();
@@ -153,7 +153,7 @@ public function testLeaveStuffAloneInStrings(string $code) {
     /**
      * @dataProvider provideTestLexNewFeatures
      */
-    public function testErrorAfterEmulation($code) {
+    public function testErrorAfterEmulation($code): void {
         $errorHandler = new ErrorHandler\Collecting();
         $lexer = $this->getLexer();
         $lexer->tokenize('<?php ' . $code . "\0", $errorHandler);
@@ -396,7 +396,7 @@ public function provideTestLexNewFeatures() {
     /**
      * @dataProvider provideTestTargetVersion
      */
-    public function testTargetVersion(string $phpVersion, string $code, array $expectedTokens) {
+    public function testTargetVersion(string $phpVersion, string $code, array $expectedTokens): void {
         $lexer = new Emulative(PhpVersion::fromString($phpVersion));
         $this->assertSameTokens($expectedTokens, $lexer->tokenize('<?php ' . $code));
     }
diff --git a/test/PhpParser/LexerTest.php b/test/PhpParser/LexerTest.php
index a6ccac679c..2f71f02997 100644
--- a/test/PhpParser/LexerTest.php
+++ b/test/PhpParser/LexerTest.php
@@ -13,7 +13,7 @@ protected function getLexer() {
     /**
      * @dataProvider provideTestError
      */
-    public function testError($code, $messages) {
+    public function testError($code, $messages): void {
         if (defined('HHVM_VERSION')) {
             $this->markTestSkipped('HHVM does not throw warnings from token_get_all()');
         }
@@ -45,7 +45,7 @@ public function provideTestError() {
         ];
     }
 
-    public function testDefaultErrorHandler() {
+    public function testDefaultErrorHandler(): void {
         $this->expectException(Error::class);
         $this->expectExceptionMessage('Unterminated comment on line 1');
         $lexer = $this->getLexer();
@@ -55,7 +55,7 @@ public function testDefaultErrorHandler() {
     /**
      * @dataProvider provideTestLex
      */
-    public function testLex($code, $expectedTokens) {
+    public function testLex($code, $expectedTokens): void {
         $lexer = $this->getLexer();
         $tokens = $lexer->tokenize($code);
         foreach ($tokens as $token) {
@@ -97,7 +97,7 @@ public function provideTestLex() {
         ];
     }
 
-    public function testGetTokens() {
+    public function testGetTokens(): void {
         $code = '<?php "a";' . "\n" . '// foo' . "\n" . '// bar' . "\n\n" . '"b";';
         $expectedTokens = [
             new Token(T_OPEN_TAG, '<?php ', 1, 0),
diff --git a/test/PhpParser/NameContextTest.php b/test/PhpParser/NameContextTest.php
index 8338cfedd2..b6474faf27 100644
--- a/test/PhpParser/NameContextTest.php
+++ b/test/PhpParser/NameContextTest.php
@@ -9,7 +9,7 @@ class NameContextTest extends \PHPUnit\Framework\TestCase {
     /**
      * @dataProvider provideTestGetPossibleNames
      */
-    public function testGetPossibleNames($type, $name, $expectedPossibleNames) {
+    public function testGetPossibleNames($type, $name, $expectedPossibleNames): void {
         $nameContext = new NameContext(new ErrorHandler\Throwing());
         $nameContext->startNamespace(new Name('NS'));
         $nameContext->addAlias(new Name('Foo'), 'Foo', Use_::TYPE_NORMAL);
diff --git a/test/PhpParser/Node/Expr/CallableLikeTest.php b/test/PhpParser/Node/Expr/CallableLikeTest.php
index 9a0349c3ac..c01bb8eb0a 100644
--- a/test/PhpParser/Node/Expr/CallableLikeTest.php
+++ b/test/PhpParser/Node/Expr/CallableLikeTest.php
@@ -11,7 +11,7 @@ class CallableLikeTest extends \PHPUnit\Framework\TestCase {
     /**
      * @dataProvider provideTestIsFirstClassCallable
      */
-    public function testIsFirstClassCallable(CallLike $node, bool $isFirstClassCallable) {
+    public function testIsFirstClassCallable(CallLike $node, bool $isFirstClassCallable): void {
         $this->assertSame($isFirstClassCallable, $node->isFirstClassCallable());
         if (!$isFirstClassCallable) {
             $this->assertSame($node->getRawArgs(), $node->getArgs());
diff --git a/test/PhpParser/Node/IdentifierTest.php b/test/PhpParser/Node/IdentifierTest.php
index 3b52806b9c..f8f328a709 100644
--- a/test/PhpParser/Node/IdentifierTest.php
+++ b/test/PhpParser/Node/IdentifierTest.php
@@ -3,12 +3,12 @@
 namespace PhpParser\Node;
 
 class IdentifierTest extends \PHPUnit\Framework\TestCase {
-    public function testConstructorThrows() {
+    public function testConstructorThrows(): void {
         self::expectException(\InvalidArgumentException::class);
         new Identifier('');
     }
 
-    public function testToString() {
+    public function testToString(): void {
         $identifier = new Identifier('Foo');
 
         $this->assertSame('Foo', (string) $identifier);
@@ -17,7 +17,7 @@ public function testToString() {
     }
 
     /** @dataProvider provideTestIsSpecialClassName */
-    public function testIsSpecialClassName($identifier, $expected) {
+    public function testIsSpecialClassName($identifier, $expected): void {
         $identifier = new Identifier($identifier);
         $this->assertSame($expected, $identifier->isSpecialClassName());
     }
diff --git a/test/PhpParser/Node/NameTest.php b/test/PhpParser/Node/NameTest.php
index 50df3624b7..262b95e2ed 100644
--- a/test/PhpParser/Node/NameTest.php
+++ b/test/PhpParser/Node/NameTest.php
@@ -3,7 +3,7 @@
 namespace PhpParser\Node;
 
 class NameTest extends \PHPUnit\Framework\TestCase {
-    public function testConstruct() {
+    public function testConstruct(): void {
         $name = new Name(['foo', 'bar']);
         $this->assertSame('foo\bar', $name->name);
 
@@ -14,7 +14,7 @@ public function testConstruct() {
         $this->assertSame('foo\bar', $name->name);
     }
 
-    public function testGet() {
+    public function testGet(): void {
         $name = new Name('foo');
         $this->assertSame('foo', $name->getFirst());
         $this->assertSame('foo', $name->getLast());
@@ -26,7 +26,7 @@ public function testGet() {
         $this->assertSame(['foo', 'bar'], $name->getParts());
     }
 
-    public function testToString() {
+    public function testToString(): void {
         $name = new Name('Foo\Bar');
 
         $this->assertSame('Foo\Bar', (string) $name);
@@ -34,7 +34,7 @@ public function testToString() {
         $this->assertSame('foo\bar', $name->toLowerString());
     }
 
-    public function testSlice() {
+    public function testSlice(): void {
         $name = new Name('foo\bar\baz');
         $this->assertEquals(new Name('foo\bar\baz'), $name->slice(0));
         $this->assertEquals(new Name('bar\baz'), $name->slice(1));
@@ -50,37 +50,37 @@ public function testSlice() {
         $this->assertNull($name->slice(-2, -2));
     }
 
-    public function testSliceOffsetTooLarge() {
+    public function testSliceOffsetTooLarge(): void {
         $this->expectException(\OutOfBoundsException::class);
         $this->expectExceptionMessage('Offset 4 is out of bounds');
         (new Name('foo\bar\baz'))->slice(4);
     }
 
-    public function testSliceOffsetTooSmall() {
+    public function testSliceOffsetTooSmall(): void {
         $this->expectException(\OutOfBoundsException::class);
         $this->expectExceptionMessage('Offset -4 is out of bounds');
         (new Name('foo\bar\baz'))->slice(-4);
     }
 
-    public function testSliceLengthTooLarge() {
+    public function testSliceLengthTooLarge(): void {
         $this->expectException(\OutOfBoundsException::class);
         $this->expectExceptionMessage('Length 4 is out of bounds');
         (new Name('foo\bar\baz'))->slice(0, 4);
     }
 
-    public function testSliceLengthTooSmall() {
+    public function testSliceLengthTooSmall(): void {
         $this->expectException(\OutOfBoundsException::class);
         $this->expectExceptionMessage('Length -4 is out of bounds');
         (new Name('foo\bar\baz'))->slice(0, -4);
     }
 
-    public function testSliceLengthTooLargeWithOffset() {
+    public function testSliceLengthTooLargeWithOffset(): void {
         $this->expectException(\OutOfBoundsException::class);
         $this->expectExceptionMessage('Length 3 is out of bounds');
         (new Name('foo\bar\baz'))->slice(1, 3);
     }
 
-    public function testConcat() {
+    public function testConcat(): void {
         $this->assertEquals(new Name('foo\bar\baz'), Name::concat('foo', 'bar\baz'));
         $this->assertEquals(
             new Name\FullyQualified('foo\bar'),
@@ -98,7 +98,7 @@ public function testConcat() {
         $this->assertNull(Name::concat(null, null));
     }
 
-    public function testNameTypes() {
+    public function testNameTypes(): void {
         $name = new Name('foo');
         $this->assertTrue($name->isUnqualified());
         $this->assertFalse($name->isQualified());
@@ -128,26 +128,26 @@ public function testNameTypes() {
         $this->assertSame('namespace\foo', $name->toCodeString());
     }
 
-    public function testInvalidArg() {
+    public function testInvalidArg(): void {
         $this->expectException(\InvalidArgumentException::class);
         $this->expectExceptionMessage('Expected string, array of parts or Name instance');
         Name::concat('foo', new \stdClass());
     }
 
-    public function testInvalidEmptyString() {
+    public function testInvalidEmptyString(): void {
         $this->expectException(\InvalidArgumentException::class);
         $this->expectExceptionMessage('Name cannot be empty');
         new Name('');
     }
 
-    public function testInvalidEmptyArray() {
+    public function testInvalidEmptyArray(): void {
         $this->expectException(\InvalidArgumentException::class);
         $this->expectExceptionMessage('Name cannot be empty');
         new Name([]);
     }
 
     /** @dataProvider provideTestIsSpecialClassName */
-    public function testIsSpecialClassName($name, $expected) {
+    public function testIsSpecialClassName($name, $expected): void {
         $name = new Name($name);
         $this->assertSame($expected, $name->isSpecialClassName());
     }
diff --git a/test/PhpParser/Node/ParamTest.php b/test/PhpParser/Node/ParamTest.php
index ac0f3e79de..23b23ae052 100644
--- a/test/PhpParser/Node/ParamTest.php
+++ b/test/PhpParser/Node/ParamTest.php
@@ -6,7 +6,7 @@
 use PhpParser\Node\Expr\Variable;
 
 class ParamTest extends \PHPUnit\Framework\TestCase {
-    public function testNoModifiers() {
+    public function testNoModifiers(): void {
         $node = new Param(new Variable('foo'));
 
         $this->assertFalse($node->isPromoted());
@@ -19,7 +19,7 @@ public function testNoModifiers() {
     /**
      * @dataProvider provideModifiers
      */
-    public function testModifiers(string $modifier) {
+    public function testModifiers(string $modifier): void {
         $node = new Param(new Variable('foo'));
         $node->flags = constant(Modifiers::class . '::' . strtoupper($modifier));
         $this->assertTrue($node->isPromoted());
diff --git a/test/PhpParser/Node/Scalar/DNumberTest.php b/test/PhpParser/Node/Scalar/DNumberTest.php
index 25212a96b1..659fc61661 100644
--- a/test/PhpParser/Node/Scalar/DNumberTest.php
+++ b/test/PhpParser/Node/Scalar/DNumberTest.php
@@ -7,7 +7,7 @@
 use PhpParser\ParserFactory;
 
 class DNumberTest extends \PHPUnit\Framework\TestCase {
-    public function testRawValue() {
+    public function testRawValue(): void {
         $parser = (new ParserFactory())->createForNewestSupportedVersion();
         $nodes = $parser->parse('<?php echo 1_234.56;');
 
diff --git a/test/PhpParser/Node/Scalar/MagicConstTest.php b/test/PhpParser/Node/Scalar/MagicConstTest.php
index 94403fb186..b7c48b3579 100644
--- a/test/PhpParser/Node/Scalar/MagicConstTest.php
+++ b/test/PhpParser/Node/Scalar/MagicConstTest.php
@@ -6,7 +6,7 @@ class MagicConstTest extends \PHPUnit\Framework\TestCase {
     /**
      * @dataProvider provideTestGetName
      */
-    public function testGetName(MagicConst $magicConst, $name) {
+    public function testGetName(MagicConst $magicConst, $name): void {
         $this->assertSame($name, $magicConst->getName());
     }
 
diff --git a/test/PhpParser/Node/Scalar/NumberTest.php b/test/PhpParser/Node/Scalar/NumberTest.php
index c9f58acda9..db63ec2d12 100644
--- a/test/PhpParser/Node/Scalar/NumberTest.php
+++ b/test/PhpParser/Node/Scalar/NumberTest.php
@@ -6,7 +6,7 @@
 use PhpParser\ParserFactory;
 
 class NumberTest extends \PHPUnit\Framework\TestCase {
-    public function testRawValue() {
+    public function testRawValue(): void {
         $parser = (new ParserFactory())->createForNewestSupportedVersion();
         $nodes = $parser->parse('<?php echo 1_234;');
 
diff --git a/test/PhpParser/Node/Scalar/StringTest.php b/test/PhpParser/Node/Scalar/StringTest.php
index 7539cc0bc7..4b2c3b222d 100644
--- a/test/PhpParser/Node/Scalar/StringTest.php
+++ b/test/PhpParser/Node/Scalar/StringTest.php
@@ -6,7 +6,7 @@
 use PhpParser\ParserFactory;
 
 class StringTest extends \PHPUnit\Framework\TestCase {
-    public function testRawValue() {
+    public function testRawValue(): void {
         $parser = (new ParserFactory())->createForNewestSupportedVersion();
         $nodes = $parser->parse('<?php echo "sequence \x41";');
 
@@ -25,7 +25,7 @@ public function testRawValue() {
     /**
      * @dataProvider provideTestParseEscapeSequences
      */
-    public function testParseEscapeSequences($expected, $string, $quote) {
+    public function testParseEscapeSequences($expected, $string, $quote): void {
         $this->assertSame(
             $expected,
             String_::parseEscapeSequences($string, $quote)
@@ -35,7 +35,7 @@ public function testParseEscapeSequences($expected, $string, $quote) {
     /**
      * @dataProvider provideTestParse
      */
-    public function testCreate($expected, $string) {
+    public function testCreate($expected, $string): void {
         $this->assertSame(
             $expected,
             String_::parse($string)
diff --git a/test/PhpParser/Node/Stmt/ClassConstTest.php b/test/PhpParser/Node/Stmt/ClassConstTest.php
index 06e93279a7..789b9a9c79 100644
--- a/test/PhpParser/Node/Stmt/ClassConstTest.php
+++ b/test/PhpParser/Node/Stmt/ClassConstTest.php
@@ -8,7 +8,7 @@ class ClassConstTest extends \PHPUnit\Framework\TestCase {
     /**
      * @dataProvider provideModifiers
      */
-    public function testModifiers($modifier) {
+    public function testModifiers($modifier): void {
         $node = new ClassConst(
             [], // invalid
             constant(Modifiers::class . '::' . strtoupper($modifier))
@@ -17,7 +17,7 @@ public function testModifiers($modifier) {
         $this->assertTrue($node->{'is' . $modifier}());
     }
 
-    public function testNoModifiers() {
+    public function testNoModifiers(): void {
         $node = new ClassConst([], 0);
 
         $this->assertTrue($node->isPublic());
diff --git a/test/PhpParser/Node/Stmt/ClassMethodTest.php b/test/PhpParser/Node/Stmt/ClassMethodTest.php
index 0679bc557a..c3f779ea99 100644
--- a/test/PhpParser/Node/Stmt/ClassMethodTest.php
+++ b/test/PhpParser/Node/Stmt/ClassMethodTest.php
@@ -11,7 +11,7 @@ class ClassMethodTest extends \PHPUnit\Framework\TestCase {
     /**
      * @dataProvider provideModifiers
      */
-    public function testModifiers($modifier) {
+    public function testModifiers($modifier): void {
         $node = new ClassMethod('foo', [
             'type' => constant(Modifiers::class . '::' . strtoupper($modifier))
         ]);
@@ -19,7 +19,7 @@ public function testModifiers($modifier) {
         $this->assertTrue($node->{'is' . $modifier}());
     }
 
-    public function testNoModifiers() {
+    public function testNoModifiers(): void {
         $node = new ClassMethod('foo', ['type' => 0]);
 
         $this->assertTrue($node->isPublic());
@@ -49,7 +49,7 @@ public function provideModifiers() {
      *
      * @param string $modifier Node type modifier
      */
-    public function testImplicitPublic(string $modifier) {
+    public function testImplicitPublic(string $modifier): void {
         $node = new ClassMethod('foo', [
             'type' => constant(Modifiers::class . '::' . strtoupper($modifier))
         ]);
@@ -70,7 +70,7 @@ public function implicitPublicModifiers() {
      *
      * @param string $name Node name
      */
-    public function testMagic(string $name) {
+    public function testMagic(string $name): void {
         $node = new ClassMethod($name);
         $this->assertTrue($node->isMagic(), 'Method should be magic');
     }
@@ -95,7 +95,7 @@ public function provideMagics() {
         ];
     }
 
-    public function testFunctionLike() {
+    public function testFunctionLike(): void {
         $param = new Param(new Variable('a'));
         $type = new Name('Foo');
         $return = new Return_(new Variable('a'));
diff --git a/test/PhpParser/Node/Stmt/ClassTest.php b/test/PhpParser/Node/Stmt/ClassTest.php
index f0295d2836..3f701b69d4 100644
--- a/test/PhpParser/Node/Stmt/ClassTest.php
+++ b/test/PhpParser/Node/Stmt/ClassTest.php
@@ -7,7 +7,7 @@
 use PhpParser\Node\Scalar\String_;
 
 class ClassTest extends \PHPUnit\Framework\TestCase {
-    public function testIsAbstract() {
+    public function testIsAbstract(): void {
         $class = new Class_('Foo', ['type' => Modifiers::ABSTRACT]);
         $this->assertTrue($class->isAbstract());
 
@@ -15,7 +15,7 @@ public function testIsAbstract() {
         $this->assertFalse($class->isAbstract());
     }
 
-    public function testIsFinal() {
+    public function testIsFinal(): void {
         $class = new Class_('Foo', ['type' => Modifiers::FINAL]);
         $this->assertTrue($class->isFinal());
 
@@ -23,7 +23,7 @@ public function testIsFinal() {
         $this->assertFalse($class->isFinal());
     }
 
-    public function testGetTraitUses() {
+    public function testGetTraitUses(): void {
         $traitUses = [
             new TraitUse([new Trait_('foo')]),
             new TraitUse([new Trait_('bar')]),
@@ -39,7 +39,7 @@ public function testGetTraitUses() {
         $this->assertSame($traitUses, $class->getTraitUses());
     }
 
-    public function testGetMethods() {
+    public function testGetMethods(): void {
         $methods = [
             new ClassMethod('foo'),
             new ClassMethod('bar'),
@@ -59,7 +59,7 @@ public function testGetMethods() {
         $this->assertSame($methods, $class->getMethods());
     }
 
-    public function testGetConstants() {
+    public function testGetConstants(): void {
         $constants = [
             new ClassConst([new \PhpParser\Node\Const_('foo', new String_('foo_value'))]),
             new ClassConst([new \PhpParser\Node\Const_('bar', new String_('bar_value'))]),
@@ -76,7 +76,7 @@ public function testGetConstants() {
         $this->assertSame($constants, $class->getConstants());
     }
 
-    public function testGetProperties() {
+    public function testGetProperties(): void {
         $properties = [
             new Property(Modifiers::PUBLIC, [new PropertyItem('foo')]),
             new Property(Modifiers::PUBLIC, [new PropertyItem('bar')]),
@@ -94,7 +94,7 @@ public function testGetProperties() {
         $this->assertSame($properties, $class->getProperties());
     }
 
-    public function testGetProperty() {
+    public function testGetProperty(): void {
         $properties = [
             $fooProp = new Property(Modifiers::PUBLIC, [new PropertyItem('foo1')]),
             $barProp = new Property(Modifiers::PUBLIC, [new PropertyItem('BAR1')]),
@@ -119,7 +119,7 @@ public function testGetProperty() {
         $this->assertNull($class->getProperty('nonExisting'));
     }
 
-    public function testGetMethod() {
+    public function testGetMethod(): void {
         $methodConstruct = new ClassMethod('__CONSTRUCT');
         $methodTest = new ClassMethod('test');
         $class = new Class_('Foo', [
diff --git a/test/PhpParser/Node/Stmt/InterfaceTest.php b/test/PhpParser/Node/Stmt/InterfaceTest.php
index 8d45e53add..5bb4a7840d 100644
--- a/test/PhpParser/Node/Stmt/InterfaceTest.php
+++ b/test/PhpParser/Node/Stmt/InterfaceTest.php
@@ -6,7 +6,7 @@
 use PhpParser\Node\Scalar\String_;
 
 class InterfaceTest extends \PHPUnit\Framework\TestCase {
-    public function testGetMethods() {
+    public function testGetMethods(): void {
         $methods = [
             new ClassMethod('foo'),
             new ClassMethod('bar'),
@@ -24,7 +24,7 @@ public function testGetMethods() {
         $this->assertSame($methods, $interface->getMethods());
     }
 
-    public function testGetConstants() {
+    public function testGetConstants(): void {
         $constants = [
             new ClassConst([new \PhpParser\Node\Const_('foo', new String_('foo_value'))]),
             new ClassConst([new \PhpParser\Node\Const_('bar', new String_('bar_value'))]),
diff --git a/test/PhpParser/Node/Stmt/PropertyTest.php b/test/PhpParser/Node/Stmt/PropertyTest.php
index 712e93199a..8279aa7add 100644
--- a/test/PhpParser/Node/Stmt/PropertyTest.php
+++ b/test/PhpParser/Node/Stmt/PropertyTest.php
@@ -8,7 +8,7 @@ class PropertyTest extends \PHPUnit\Framework\TestCase {
     /**
      * @dataProvider provideModifiers
      */
-    public function testModifiers($modifier) {
+    public function testModifiers($modifier): void {
         $node = new Property(
             constant(Modifiers::class . '::' . strtoupper($modifier)),
             [] // invalid
@@ -17,7 +17,7 @@ public function testModifiers($modifier) {
         $this->assertTrue($node->{'is' . $modifier}());
     }
 
-    public function testNoModifiers() {
+    public function testNoModifiers(): void {
         $node = new Property(0, []);
 
         $this->assertTrue($node->isPublic());
@@ -27,7 +27,7 @@ public function testNoModifiers() {
         $this->assertFalse($node->isReadonly());
     }
 
-    public function testStaticImplicitlyPublic() {
+    public function testStaticImplicitlyPublic(): void {
         $node = new Property(Modifiers::STATIC, []);
         $this->assertTrue($node->isPublic());
         $this->assertFalse($node->isProtected());
diff --git a/test/PhpParser/NodeAbstractTest.php b/test/PhpParser/NodeAbstractTest.php
index 3e7952aa5c..2b7c1f8cd9 100644
--- a/test/PhpParser/NodeAbstractTest.php
+++ b/test/PhpParser/NodeAbstractTest.php
@@ -75,7 +75,7 @@ public function testConstruct(array $attributes, Node $node) {
     /**
      * @dataProvider provideNodes
      */
-    public function testGetDocComment(array $attributes, Node $node) {
+    public function testGetDocComment(array $attributes, Node $node): void {
         $this->assertSame('/** doc comment */', $node->getDocComment()->getText());
         $comments = $node->getComments();
 
@@ -88,7 +88,7 @@ public function testGetDocComment(array $attributes, Node $node) {
         $this->assertNull($node->getDocComment());
     }
 
-    public function testSetDocComment() {
+    public function testSetDocComment(): void {
         $node = new DummyNode(null, null, null, []);
 
         // Add doc comment to node without comments
@@ -119,7 +119,7 @@ public function testSetDocComment() {
     /**
      * @dataProvider provideNodes
      */
-    public function testChange(array $attributes, DummyNode $node) {
+    public function testChange(array $attributes, DummyNode $node): void {
         // direct modification
         $node->subNode1 = 'newValue';
         $this->assertSame('newValue', $node->subNode1);
@@ -137,7 +137,7 @@ public function testChange(array $attributes, DummyNode $node) {
     /**
      * @dataProvider provideNodes
      */
-    public function testIteration(array $attributes, Node $node) {
+    public function testIteration(array $attributes, Node $node): void {
         // Iteration is simple object iteration over properties,
         // not over subnodes
         $i = 0;
@@ -159,7 +159,7 @@ public function testIteration(array $attributes, Node $node) {
         $this->assertSame(3, $i);
     }
 
-    public function testAttributes() {
+    public function testAttributes(): void {
         /** @var $node Node */
         $node = $this->getMockForAbstractClass(NodeAbstract::class);
 
@@ -201,7 +201,7 @@ public function testAttributes() {
         );
     }
 
-    public function testJsonSerialization() {
+    public function testJsonSerialization(): void {
         $code = <<<'PHP'
 <?php
 // comment
diff --git a/test/PhpParser/NodeDumperTest.php b/test/PhpParser/NodeDumperTest.php
index e92d5886b2..8b21948e37 100644
--- a/test/PhpParser/NodeDumperTest.php
+++ b/test/PhpParser/NodeDumperTest.php
@@ -10,7 +10,7 @@ private function canonicalize($string) {
     /**
      * @dataProvider provideTestDump
      */
-    public function testDump($node, $dump) {
+    public function testDump($node, $dump): void {
         $dumper = new NodeDumper();
 
         $this->assertSame($this->canonicalize($dump), $this->canonicalize($dumper->dump($node)));
@@ -57,7 +57,7 @@ public function provideTestDump() {
         ];
     }
 
-    public function testDumpWithPositions() {
+    public function testDumpWithPositions(): void {
         $parser = (new ParserFactory())->createForHostVersion();
         $dumper = new NodeDumper(['dumpPositions' => true]);
 
@@ -90,7 +90,7 @@ public function testDumpWithPositions() {
         $this->assertSame($this->canonicalize($expected), $this->canonicalize($dump));
     }
 
-    public function testError() {
+    public function testError(): void {
         $this->expectException(\InvalidArgumentException::class);
         $this->expectExceptionMessage('Can only dump nodes and arrays.');
         $dumper = new NodeDumper();
diff --git a/test/PhpParser/NodeFinderTest.php b/test/PhpParser/NodeFinderTest.php
index dd0641edbd..2929c5f869 100644
--- a/test/PhpParser/NodeFinderTest.php
+++ b/test/PhpParser/NodeFinderTest.php
@@ -14,7 +14,7 @@ private function getStmtsAndVars() {
         return [$stmts, $vars];
     }
 
-    public function testFind() {
+    public function testFind(): void {
         $finder = new NodeFinder();
         list($stmts, $vars) = $this->getStmtsAndVars();
         $varFilter = function (Node $node) {
@@ -29,7 +29,7 @@ public function testFind() {
         $this->assertSame([], $finder->find($stmts, $noneFilter));
     }
 
-    public function testFindInstanceOf() {
+    public function testFindInstanceOf(): void {
         $finder = new NodeFinder();
         list($stmts, $vars) = $this->getStmtsAndVars();
         $this->assertSame($vars, $finder->findInstanceOf($stmts, Expr\Variable::class));
@@ -37,7 +37,7 @@ public function testFindInstanceOf() {
         $this->assertSame([], $finder->findInstanceOf($stmts, Expr\BinaryOp\Mul::class));
     }
 
-    public function testFindFirst() {
+    public function testFindFirst(): void {
         $finder = new NodeFinder();
         list($stmts, $vars) = $this->getStmtsAndVars();
         $varFilter = function (Node $node) {
@@ -52,7 +52,7 @@ public function testFindFirst() {
         $this->assertNull($finder->findFirst($stmts, $noneFilter));
     }
 
-    public function testFindFirstInstanceOf() {
+    public function testFindFirstInstanceOf(): void {
         $finder = new NodeFinder();
         list($stmts, $vars) = $this->getStmtsAndVars();
         $this->assertSame($vars[0], $finder->findFirstInstanceOf($stmts, Expr\Variable::class));
diff --git a/test/PhpParser/NodeTraverserTest.php b/test/PhpParser/NodeTraverserTest.php
index 255741da2c..bc84600b6c 100644
--- a/test/PhpParser/NodeTraverserTest.php
+++ b/test/PhpParser/NodeTraverserTest.php
@@ -9,7 +9,7 @@
 use PhpParser\Node\Stmt\If_;
 
 class NodeTraverserTest extends \PHPUnit\Framework\TestCase {
-    public function testNonModifying() {
+    public function testNonModifying(): void {
         $str1Node = new String_('Foo');
         $str2Node = new String_('Bar');
         $echoNode = new Node\Stmt\Echo_([$str1Node, $str2Node]);
@@ -32,7 +32,7 @@ public function testNonModifying() {
         ], $visitor->trace);
     }
 
-    public function testModifying() {
+    public function testModifying(): void {
         $str1Node  = new String_('Foo');
         $str2Node  = new String_('Bar');
         $printNode = new Expr\Print_($str1Node);
@@ -75,7 +75,7 @@ public function testModifying() {
         ], $visitor3->trace);
     }
 
-    public function testRemoveFromLeave() {
+    public function testRemoveFromLeave(): void {
         $str1Node = new String_('Foo');
         $str2Node = new String_('Bar');
 
@@ -99,7 +99,7 @@ public function testRemoveFromLeave() {
         ], $visitor2->trace);
     }
 
-    public function testRemoveFromEnter() {
+    public function testRemoveFromEnter(): void {
         $str1Node = new String_('Foo');
         $str2Node = new String_('Bar');
 
@@ -122,7 +122,7 @@ public function testRemoveFromEnter() {
         ], $visitor2->trace);
     }
 
-    public function testReturnArrayFromEnter() {
+    public function testReturnArrayFromEnter(): void {
         $str1Node = new String_('Str1');
         $str2Node = new String_('Str2');
         $str3Node = new String_('Str3');
@@ -147,7 +147,7 @@ public function testReturnArrayFromEnter() {
         ], $visitor2->trace);
     }
 
-    public function testMerge() {
+    public function testMerge(): void {
         $strStart  = new String_('Start');
         $strMiddle = new String_('End');
         $strEnd    = new String_('Middle');
@@ -167,7 +167,7 @@ public function testMerge() {
         );
     }
 
-    public function testInvalidDeepArray() {
+    public function testInvalidDeepArray(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Invalid node structure: Contains nested arrays');
         $strNode = new String_('Foo');
@@ -177,7 +177,7 @@ public function testInvalidDeepArray() {
         $this->assertEquals($stmts, $traverser->traverse($stmts));
     }
 
-    public function testDontTraverseChildren() {
+    public function testDontTraverseChildren(): void {
         $strNode = new String_('str');
         $printNode = new Expr\Print_($strNode);
         $varNode = new Expr\Variable('foo');
@@ -212,7 +212,7 @@ public function testDontTraverseChildren() {
         $this->assertEquals($expectedTrace, $visitor2->trace);
     }
 
-    public function testDontTraverseCurrentAndChildren() {
+    public function testDontTraverseCurrentAndChildren(): void {
         // print 'str'; -($foo * $foo);
         $strNode = new String_('str');
         $printNode = new Expr\Print_($strNode);
@@ -254,7 +254,7 @@ public function testDontTraverseCurrentAndChildren() {
         ], $visitor2->trace);
     }
 
-    public function testStopTraversal() {
+    public function testStopTraversal(): void {
         $varNode1 = new Expr\Variable('a');
         $varNode2 = new Expr\Variable('b');
         $varNode3 = new Expr\Variable('c');
@@ -343,7 +343,7 @@ public function testStopTraversal() {
         ], $visitor->trace);
     }
 
-    public function testReplaceWithNull() {
+    public function testReplaceWithNull(): void {
         $one = new Int_(1);
         $else1 = new Else_();
         $else2 = new Else_();
@@ -381,7 +381,7 @@ public function testReplaceWithNull() {
         ], $visitor2->trace);
     }
 
-    public function testRemovingVisitor() {
+    public function testRemovingVisitor(): void {
         $visitor1 = new class () extends NodeVisitorAbstract {};
         $visitor2 = new class () extends NodeVisitorAbstract {};
         $visitor3 = new class () extends NodeVisitorAbstract {};
@@ -404,7 +404,7 @@ public function testRemovingVisitor() {
         $this->assertSame($postExpected, $getVisitors());
     }
 
-    public function testNoCloneNodes() {
+    public function testNoCloneNodes(): void {
         $stmts = [new Node\Stmt\Echo_([new String_('Foo'), new String_('Bar')])];
 
         $traverser = new NodeTraverser();
@@ -415,7 +415,7 @@ public function testNoCloneNodes() {
     /**
      * @dataProvider provideTestInvalidReturn
      */
-    public function testInvalidReturn($stmts, $visitor, $message) {
+    public function testInvalidReturn($stmts, $visitor, $message): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage($message);
 
diff --git a/test/PhpParser/NodeVisitor/FindingVisitorTest.php b/test/PhpParser/NodeVisitor/FindingVisitorTest.php
index 4295249c9d..195074f1b0 100644
--- a/test/PhpParser/NodeVisitor/FindingVisitorTest.php
+++ b/test/PhpParser/NodeVisitor/FindingVisitorTest.php
@@ -7,7 +7,7 @@
 use PhpParser\NodeTraverser;
 
 class FindingVisitorTest extends \PHPUnit\Framework\TestCase {
-    public function testFindVariables() {
+    public function testFindVariables(): void {
         $traverser = new NodeTraverser();
         $visitor = new FindingVisitor(function (Node $node) {
             return $node instanceof Node\Expr\Variable;
@@ -27,7 +27,7 @@ public function testFindVariables() {
         ], $visitor->getFoundNodes());
     }
 
-    public function testFindAll() {
+    public function testFindAll(): void {
         $traverser = new NodeTraverser();
         $visitor = new FindingVisitor(function (Node $node) {
             return true; // All nodes
diff --git a/test/PhpParser/NodeVisitor/FirstFindingVisitorTest.php b/test/PhpParser/NodeVisitor/FirstFindingVisitorTest.php
index b79e270f42..2163d9d470 100644
--- a/test/PhpParser/NodeVisitor/FirstFindingVisitorTest.php
+++ b/test/PhpParser/NodeVisitor/FirstFindingVisitorTest.php
@@ -7,7 +7,7 @@
 use PhpParser\NodeTraverser;
 
 class FirstFindingVisitorTest extends \PHPUnit\Framework\TestCase {
-    public function testFindFirstVariable() {
+    public function testFindFirstVariable(): void {
         $traverser = new NodeTraverser();
         $visitor = new FirstFindingVisitor(function (Node $node) {
             return $node instanceof Node\Expr\Variable;
@@ -21,7 +21,7 @@ public function testFindFirstVariable() {
         $this->assertSame($assign->var, $visitor->getFoundNode());
     }
 
-    public function testFindNone() {
+    public function testFindNone(): void {
         $traverser = new NodeTraverser();
         $visitor = new FirstFindingVisitor(function (Node $node) {
             return $node instanceof Node\Expr\BinaryOp;
diff --git a/test/PhpParser/NodeVisitor/NameResolverTest.php b/test/PhpParser/NodeVisitor/NameResolverTest.php
index b0065968c7..449051fbf6 100644
--- a/test/PhpParser/NodeVisitor/NameResolverTest.php
+++ b/test/PhpParser/NodeVisitor/NameResolverTest.php
@@ -16,7 +16,7 @@ private function canonicalize($string) {
     /**
      * @covers \PhpParser\NodeVisitor\NameResolver
      */
-    public function testResolveNames() {
+    public function testResolveNames(): void {
         $code = <<<'EOC'
 <?php
 
@@ -176,7 +176,7 @@ public function testResolveNames() {
     /**
      * @covers \PhpParser\NodeVisitor\NameResolver
      */
-    public function testResolveLocations() {
+    public function testResolveLocations(): void {
         $code = <<<'EOC'
 <?php
 namespace NS;
@@ -328,7 +328,7 @@ function fn4(?array $a): ?array
         );
     }
 
-    public function testNoResolveSpecialName() {
+    public function testNoResolveSpecialName(): void {
         $stmts = [new Node\Expr\New_(new Name('self'))];
 
         $traverser = new PhpParser\NodeTraverser();
@@ -337,7 +337,7 @@ public function testNoResolveSpecialName() {
         $this->assertEquals($stmts, $traverser->traverse($stmts));
     }
 
-    public function testAddDeclarationNamespacedName() {
+    public function testAddDeclarationNamespacedName(): void {
         $nsStmts = [
             new Stmt\Class_('A'),
             new Stmt\Interface_('B'),
@@ -372,7 +372,7 @@ public function testAddDeclarationNamespacedName() {
         $this->assertSame('F', (string) $stmts[0]->stmts[6]->namespacedName);
     }
 
-    public function testAddRuntimeResolvedNamespacedName() {
+    public function testAddRuntimeResolvedNamespacedName(): void {
         $stmts = [
             new Stmt\Namespace_(new Name('NS'), [
                 new Expr\FuncCall(new Name('foo')),
@@ -398,7 +398,7 @@ public function testAddRuntimeResolvedNamespacedName() {
     /**
      * @dataProvider provideTestError
      */
-    public function testError(Node $stmt, $errorMsg) {
+    public function testError(Node $stmt, $errorMsg): void {
         $this->expectException(\PhpParser\Error::class);
         $this->expectExceptionMessage($errorMsg);
 
@@ -449,7 +449,7 @@ public function provideTestError() {
         ];
     }
 
-    public function testClassNameIsCaseInsensitive() {
+    public function testClassNameIsCaseInsensitive(): void {
         $source = <<<'EOC'
 <?php
 namespace Foo;
@@ -470,7 +470,7 @@ public function testClassNameIsCaseInsensitive() {
         $this->assertSame('Bar\\Baz', $assign->expr->class->name);
     }
 
-    public function testSpecialClassNamesAreCaseInsensitive() {
+    public function testSpecialClassNamesAreCaseInsensitive(): void {
         $source = <<<'EOC'
 <?php
 namespace Foo;
@@ -501,7 +501,7 @@ public static function method()
         $this->assertSame('STATIC', (string) $methodStmt->stmts[2]->expr->class);
     }
 
-    public function testAddOriginalNames() {
+    public function testAddOriginalNames(): void {
         $traverser = new PhpParser\NodeTraverser();
         $traverser->addVisitor(new NameResolver(null, ['preserveOriginalNames' => true]));
 
@@ -520,7 +520,7 @@ public function testAddOriginalNames() {
         $this->assertSame($n2, $stmts[0]->stmts[1]->name->getAttribute('originalName'));
     }
 
-    public function testAttributeOnlyMode() {
+    public function testAttributeOnlyMode(): void {
         $traverser = new PhpParser\NodeTraverser();
         $traverser->addVisitor(new NameResolver(null, ['replaceNodes' => false]));
 
diff --git a/test/PhpParser/NodeVisitor/NodeConnectingVisitorTest.php b/test/PhpParser/NodeVisitor/NodeConnectingVisitorTest.php
index 3dcb2b45a4..eab58776cd 100644
--- a/test/PhpParser/NodeVisitor/NodeConnectingVisitorTest.php
+++ b/test/PhpParser/NodeVisitor/NodeConnectingVisitorTest.php
@@ -10,7 +10,7 @@
 use PhpParser\ParserFactory;
 
 final class NodeConnectingVisitorTest extends \PHPUnit\Framework\TestCase {
-    public function testConnectsNodeToItsParentNodeAndItsSiblingNodes() {
+    public function testConnectsNodeToItsParentNodeAndItsSiblingNodes(): void {
         $ast = (new ParserFactory())->createForNewestSupportedVersion()->parse(
             '<?php if (true) {} else {}'
         );
diff --git a/test/PhpParser/NodeVisitor/ParentConnectingVisitorTest.php b/test/PhpParser/NodeVisitor/ParentConnectingVisitorTest.php
index 96e0748e9b..8f66a36479 100644
--- a/test/PhpParser/NodeVisitor/ParentConnectingVisitorTest.php
+++ b/test/PhpParser/NodeVisitor/ParentConnectingVisitorTest.php
@@ -8,7 +8,7 @@
 use PhpParser\ParserFactory;
 
 final class ParentConnectingVisitorTest extends \PHPUnit\Framework\TestCase {
-    public function testConnectsChildNodeToParentNode() {
+    public function testConnectsChildNodeToParentNode(): void {
         $ast = (new ParserFactory())->createForNewestSupportedVersion()->parse(
             '<?php class C { public function m() {} }'
         );
diff --git a/test/PhpParser/ParserFactoryTest.php b/test/PhpParser/ParserFactoryTest.php
index e0f5697a1d..7108d9e00a 100644
--- a/test/PhpParser/ParserFactoryTest.php
+++ b/test/PhpParser/ParserFactoryTest.php
@@ -9,7 +9,7 @@
 use PhpParser\Parser\Php8;
 
 class ParserFactoryTest extends \PHPUnit\Framework\TestCase {
-    public function testCreate() {
+    public function testCreate(): void {
         $factory = new ParserFactory();
         $this->assertInstanceOf(Php8::class, $factory->createForNewestSupportedVersion());
         $this->assertInstanceOf(Parser::class, $factory->createForHostVersion());
diff --git a/test/PhpParser/ParserTest.php b/test/PhpParser/ParserTest.php
index 48f5ffe8e5..8096685901 100644
--- a/test/PhpParser/ParserTest.php
+++ b/test/PhpParser/ParserTest.php
@@ -11,28 +11,28 @@ abstract class ParserTest extends \PHPUnit\Framework\TestCase {
     /** @returns Parser */
     abstract protected function getParser(Lexer $lexer);
 
-    public function testParserThrowsSyntaxError() {
+    public function testParserThrowsSyntaxError(): void {
         $this->expectException(Error::class);
         $this->expectExceptionMessage('Syntax error, unexpected EOF on line 1');
         $parser = $this->getParser(new Lexer());
         $parser->parse('<?php foo');
     }
 
-    public function testParserThrowsSpecialError() {
+    public function testParserThrowsSpecialError(): void {
         $this->expectException(Error::class);
         $this->expectExceptionMessage('Cannot use foo as self because \'self\' is a special class name on line 1');
         $parser = $this->getParser(new Lexer());
         $parser->parse('<?php use foo as self;');
     }
 
-    public function testParserThrowsLexerError() {
+    public function testParserThrowsLexerError(): void {
         $this->expectException(Error::class);
         $this->expectExceptionMessage('Unterminated comment on line 1');
         $parser = $this->getParser(new Lexer());
         $parser->parse('<?php /*');
     }
 
-    public function testAttributeAssignment() {
+    public function testAttributeAssignment(): void {
         $lexer = new Lexer();
 
         $code = <<<'EOC'
@@ -107,7 +107,7 @@ function test($a) {
         ], $var->getAttributes());
     }
 
-    public function testInvalidToken() {
+    public function testInvalidToken(): void {
         $this->expectException(\RangeException::class);
         $this->expectExceptionMessage('The lexer returned an invalid token (id=999, value=foobar)');
         $lexer = new InvalidTokenLexer();
@@ -118,7 +118,7 @@ public function testInvalidToken() {
     /**
      * @dataProvider provideTestExtraAttributes
      */
-    public function testExtraAttributes($code, $expectedAttributes) {
+    public function testExtraAttributes($code, $expectedAttributes): void {
         $parser = $this->getParser(new Lexer\Emulative());
         $stmts = $parser->parse("<?php $code;");
         $node = $stmts[0] instanceof Stmt\Expression ? $stmts[0]->expr : $stmts[0];
@@ -180,7 +180,7 @@ public function provideTestExtraAttributes() {
         ];
     }
 
-    public function testListKindAttribute() {
+    public function testListKindAttribute(): void {
         $parser = $this->getParser(new Lexer\Emulative());
         $stmts = $parser->parse('<?php list(list($x)) = $y; [[$x]] = $y;');
         $this->assertSame($stmts[0]->expr->var->getAttribute('kind'), Expr\List_::KIND_LIST);
@@ -189,7 +189,7 @@ public function testListKindAttribute() {
         $this->assertSame($stmts[1]->expr->var->items[0]->value->getAttribute('kind'), Expr\List_::KIND_ARRAY);
     }
 
-    public function testGetTokens() {
+    public function testGetTokens(): void {
         $lexer = new Lexer();
         $parser = $this->getParser($lexer);
         $parser->parse('<?php echo "Foo";');
diff --git a/test/PhpParser/PhpVersionTest.php b/test/PhpParser/PhpVersionTest.php
index c5d2abea46..cacc0f41b8 100644
--- a/test/PhpParser/PhpVersionTest.php
+++ b/test/PhpParser/PhpVersionTest.php
@@ -3,7 +3,7 @@
 namespace PhpParser;
 
 class PhpVersionTest extends \PHPUnit\Framework\TestCase {
-    public function testConstruction() {
+    public function testConstruction(): void {
         $version = PhpVersion::fromComponents(8, 2);
         $this->assertSame(80200, $version->id);
 
@@ -17,13 +17,13 @@ public function testConstruction() {
         $this->assertSame(80200, $version->id);
     }
 
-    public function testInvalidVersion() {
+    public function testInvalidVersion(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Invalid PHP version "8"');
         PhpVersion::fromString('8');
     }
 
-    public function testEquals() {
+    public function testEquals(): void {
         $php74 = PhpVersion::fromComponents(7, 4);
         $php81 = PhpVersion::fromComponents(8, 1);
         $php82 = PhpVersion::fromComponents(8, 2);
diff --git a/test/PhpParser/PrettyPrinterTest.php b/test/PhpParser/PrettyPrinterTest.php
index 9af5510ca7..a937d74978 100644
--- a/test/PhpParser/PrettyPrinterTest.php
+++ b/test/PhpParser/PrettyPrinterTest.php
@@ -29,14 +29,14 @@ protected function doTestPrettyPrintMethod($method, $name, $code, $expected, $mo
     /**
      * @dataProvider provideTestPrettyPrint
      */
-    public function testPrettyPrint($name, $code, $expected, $mode) {
+    public function testPrettyPrint($name, $code, $expected, $mode): void {
         $this->doTestPrettyPrintMethod('prettyPrint', $name, $code, $expected, $mode);
     }
 
     /**
      * @dataProvider provideTestPrettyPrintFile
      */
-    public function testPrettyPrintFile($name, $code, $expected, $mode) {
+    public function testPrettyPrintFile($name, $code, $expected, $mode): void {
         $this->doTestPrettyPrintMethod('prettyPrintFile', $name, $code, $expected, $mode);
     }
 
@@ -48,7 +48,7 @@ public function provideTestPrettyPrintFile() {
         return $this->getTests(__DIR__ . '/../code/prettyPrinter', 'file-test');
     }
 
-    public function testPrettyPrintExpr() {
+    public function testPrettyPrintExpr(): void {
         $prettyPrinter = new Standard();
         $expr = new Expr\BinaryOp\Mul(
             new Expr\BinaryOp\Plus(new Expr\Variable('a'), new Expr\Variable('b')),
@@ -62,7 +62,7 @@ public function testPrettyPrintExpr() {
         $this->assertEquals("function () {\n    return 'a\nb';\n}", $prettyPrinter->prettyPrintExpr($expr));
     }
 
-    public function testCommentBeforeInlineHTML() {
+    public function testCommentBeforeInlineHTML(): void {
         $prettyPrinter = new PrettyPrinter\Standard();
         $comment = new Comment\Doc("/**\n * This is a comment\n */");
         $stmts = [new Stmt\InlineHTML('Hello World!', ['comments' => [$comment]])];
@@ -70,7 +70,7 @@ public function testCommentBeforeInlineHTML() {
         $this->assertSame($expected, $prettyPrinter->prettyPrintFile($stmts));
     }
 
-    public function testArraySyntaxDefault() {
+    public function testArraySyntaxDefault(): void {
         $prettyPrinter = new Standard(['shortArraySyntax' => true]);
         $expr = new Expr\Array_([
             new Node\ArrayItem(new String_('val'), new String_('key'))
@@ -82,7 +82,7 @@ public function testArraySyntaxDefault() {
     /**
      * @dataProvider provideTestKindAttributes
      */
-    public function testKindAttributes($node, $expected) {
+    public function testKindAttributes($node, $expected): void {
         $prttyPrinter = new PrettyPrinter\Standard();
         $result = $prttyPrinter->prettyPrintExpr($node);
         $this->assertSame($expected, $result);
@@ -138,7 +138,7 @@ public function provideTestKindAttributes() {
     }
 
     /** @dataProvider provideTestUnnaturalLiterals */
-    public function testUnnaturalLiterals($node, $expected) {
+    public function testUnnaturalLiterals($node, $expected): void {
         $prttyPrinter = new PrettyPrinter\Standard();
         $result = $prttyPrinter->prettyPrintExpr($node);
         $this->assertSame($expected, $result);
@@ -157,7 +157,7 @@ public function provideTestUnnaturalLiterals() {
         ];
     }
 
-    public function testPrettyPrintWithError() {
+    public function testPrettyPrintWithError(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Cannot pretty-print AST with Error nodes');
         $stmts = [new Stmt\Expression(
@@ -167,7 +167,7 @@ public function testPrettyPrintWithError() {
         $prettyPrinter->prettyPrint($stmts);
     }
 
-    public function testPrettyPrintWithErrorInClassConstFetch() {
+    public function testPrettyPrintWithErrorInClassConstFetch(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Cannot pretty-print AST with Error nodes');
         $stmts = [new Stmt\Expression(
@@ -180,7 +180,7 @@ public function testPrettyPrintWithErrorInClassConstFetch() {
     /**
      * @dataProvider provideTestFormatPreservingPrint
      */
-    public function testFormatPreservingPrint($name, $code, $modification, $expected, $modeLine) {
+    public function testFormatPreservingPrint($name, $code, $modification, $expected, $modeLine): void {
         $lexer = new Lexer\Emulative();
         $parser = new Parser\Php7($lexer);
         $traverser = new NodeTraverser(new NodeVisitor\CloningVisitor());
@@ -216,7 +216,7 @@ public function provideTestFormatPreservingPrint() {
     /**
      * @dataProvider provideTestRoundTripPrint
      */
-    public function testRoundTripPrint($name, $code, $expected, $modeLine) {
+    public function testRoundTripPrint($name, $code, $expected, $modeLine): void {
         /**
          * This test makes sure that the format-preserving pretty printer round-trips for all
          * the pretty printer tests (i.e. returns the input if no changes occurred).
@@ -252,7 +252,7 @@ public function provideTestRoundTripPrint() {
         );
     }
 
-    public function testWindowsNewline() {
+    public function testWindowsNewline(): void {
         $prettyPrinter = new Standard([
             'newline' => "\r\n",
             'phpVersion' => PhpVersion::fromComponents(7, 2),
@@ -294,7 +294,7 @@ public function testWindowsNewline() {
             $code);
     }
 
-    public function testInvalidNewline() {
+    public function testInvalidNewline(): void {
         $this->expectException(\LogicException::class);
         $this->expectExceptionMessage('Option "newline" must be one of "\n" or "\r\n"');
         new PrettyPrinter\Standard(['newline' => 'foo']);
diff --git a/test/PhpParser/TokenTest.php b/test/PhpParser/TokenTest.php
index 30787e686d..8297699c6e 100644
--- a/test/PhpParser/TokenTest.php
+++ b/test/PhpParser/TokenTest.php
@@ -3,14 +3,14 @@
 namespace PhpParser;
 
 class TokenTest extends \PHPUnit\Framework\TestCase {
-    public function testGetTokenName() {
+    public function testGetTokenName(): void {
         $token = new Token(\ord(','), ',');
         $this->assertSame(',', $token->getTokenName());
         $token = new Token(\T_WHITESPACE, ' ');
         $this->assertSame('T_WHITESPACE', $token->getTokenName());
     }
 
-    public function testIs() {
+    public function testIs(): void {
         $token = new Token(\ord(','), ',');
         $this->assertTrue($token->is(\ord(',')));
         $this->assertFalse($token->is(\ord(';')));
@@ -23,7 +23,7 @@ public function testIs() {
     }
 
     /** @dataProvider provideTestIsIgnorable */
-    public function testIsIgnorable(int $id, string $text, bool $isIgnorable) {
+    public function testIsIgnorable(int $id, string $text, bool $isIgnorable): void {
         $token = new Token($id, $text);
         $this->assertSame($isIgnorable, $token->isIgnorable());
     }
@@ -38,7 +38,7 @@ public function provideTestIsIgnorable() {
         ];
     }
 
-    public function testToString() {
+    public function testToString(): void {
         $token = new Token(\ord(','), ',');
         $this->assertSame(',', (string) $token);
         $token = new Token(\T_STRING, 'foo');
diff --git a/tools/fuzzing/target.php b/tools/fuzzing/target.php
index 6a7b3ebc27..8cbd619c16 100644
--- a/tools/fuzzing/target.php
+++ b/tools/fuzzing/target.php
@@ -39,11 +39,11 @@
     private $tokens;
     public $hasProblematicConstruct;
 
-    public function setTokens(array $tokens) {
+    public function setTokens(array $tokens): void {
         $this->tokens = $tokens;
     }
 
-    public function beforeTraverse(array $nodes) {
+    public function beforeTraverse(array $nodes): void {
         $this->hasProblematicConstruct = false;
     }