diff --git a/.phpstan.neon b/.phpstan.neon
index 8136274..c8c69be 100644
--- a/.phpstan.neon
+++ b/.phpstan.neon
@@ -1,11 +1,15 @@
 # SPDX-FileCopyrightText: 2015-2023 Artur Weigandt https://wlabs.de/kontakt
 # SPDX-License-Identifier: GPL-3.0-or-later
 
+includes:
+	- vendor/phpstan/phpstan-phpunit/extension.neon
+
 parameters:
 	level: 8
 
 	paths:
 		- src/
+		- tests/
 
 	scanDirectories:
 		- vendor
diff --git a/composer.json b/composer.json
index 82738e1..48f9de4 100644
--- a/composer.json
+++ b/composer.json
@@ -18,6 +18,7 @@
     "require-dev": {
         "friendsofphp/php-cs-fixer": "^3.35",
         "phpstan/phpstan": "^1.10",
+        "phpstan/phpstan-phpunit": "^1.3",
         "phpunit/phpunit": "^9 || ^10"
     },
     "autoload": {
diff --git a/tests/Fixtures/Factory.php b/tests/Fixtures/Factory.php
index b6d916c..a37e838 100644
--- a/tests/Fixtures/Factory.php
+++ b/tests/Fixtures/Factory.php
@@ -8,7 +8,7 @@
 
 namespace Art4\JsonApiClient\Tests\Fixtures;
 
-use Art4\JsonApiClient\Utils\FactoryInterface;
+use Art4\JsonApiClient\Factory as FactoryInterface;
 
 final class Factory implements FactoryInterface
 {
diff --git a/tests/Fixtures/HelperTrait.php b/tests/Fixtures/HelperTrait.php
index 94cc0d1..aefbb70 100644
--- a/tests/Fixtures/HelperTrait.php
+++ b/tests/Fixtures/HelperTrait.php
@@ -12,22 +12,26 @@
 use Art4\JsonApiClient\Factory;
 use Art4\JsonApiClient\Manager;
 use Art4\JsonApiClient\Tests\Fixtures\Factory as FixtureFactory;
+use PHPUnit\Framework\MockObject\MockObject;
 
 /**
  * Helper Trait
  */
 trait HelperTrait
 {
+    /** @var Manager&MockObject */
     protected Manager $manager;
 
+    /** @var Factory&MockObject */
     protected Factory $factory;
 
+    /** @var Accessable&MockObject */
     protected Accessable $parent;
 
     /**
      * Json Values Provider
      *
-     * @see http://json.org/
+     * @return array<array<mixed>>
      */
     public static function jsonValuesProvider(): array
     {
@@ -47,7 +51,7 @@ public static function jsonValuesProvider(): array
     /**
      * Json Values Provider but without the object
      *
-     * @see http://json.org/
+     * @return array<array<mixed>>
      */
     public static function jsonValuesProviderWithoutObject(): array
     {
@@ -61,7 +65,7 @@ public static function jsonValuesProviderWithoutObject(): array
     /**
      * Json Values Provider but without the array
      *
-     * @see http://json.org/
+     * @return array<array<mixed>>
      */
     public static function jsonValuesProviderWithoutArray(): array
     {
@@ -75,7 +79,7 @@ public static function jsonValuesProviderWithoutArray(): array
     /**
      * Json Values Provider but without the string
      *
-     * @see http://json.org/
+     * @return array<array<mixed>>
      */
     public static function jsonValuesProviderWithoutString(): array
     {
@@ -89,7 +93,7 @@ public static function jsonValuesProviderWithoutString(): array
     /**
      * Json Values Provider but without the object and string
      *
-     * @see http://json.org/
+     * @return array<array<mixed>>
      */
     public static function jsonValuesProviderWithoutObjectAndString(): array
     {
@@ -104,7 +108,7 @@ public static function jsonValuesProviderWithoutObjectAndString(): array
     /**
      * Json Values as string Provider
      *
-     * @see http://json.org/
+     * @return array<array<string>>
      */
     public static function jsonValuesAsStringProvider(): array
     {
@@ -124,7 +128,7 @@ public static function jsonValuesAsStringProvider(): array
     /**
      * Json Values as string Provider but without the object
      *
-     * @see http://json.org/
+     * @return array<array<string>>
      */
     public static function jsonValuesAsStringProviderWithoutObject(): array
     {
@@ -145,7 +149,7 @@ public function buildManagerMock()
         $factory->testcase = $this;
 
         // Mock Manager
-        $manager = $this->createMock('Art4\JsonApiClient\Utils\FactoryManagerInterface');
+        $manager = $this->createMock(Manager::class);
 
         $manager->expects($this->any())
             ->method('getFactory')