diff --git a/tests/Models/NullProjectAttributeTest.php b/tests/Models/NullProjectAttributeTest.php
new file mode 100644
index 0000000..cf01d8e
--- /dev/null
+++ b/tests/Models/NullProjectAttributeTest.php
@@ -0,0 +1,52 @@
+<?php
+/**
+ * Jingga
+ *
+ * PHP Version 8.1
+ *
+ * @package   tests
+ * @copyright Dennis Eichhorn
+ * @license   OMS License 2.0
+ * @version   1.0.0
+ * @link      https://jingga.app
+ */
+declare(strict_types=1);
+
+namespace Modules\ProjectManagement\tests\Models;
+
+use Modules\ProjectManagement\Models\NullProjectAttribute;
+
+/**
+ * @internal
+ */
+final class NullProjectAttributeTest extends \PHPUnit\Framework\TestCase
+{
+    /**
+     * @covers Modules\ProjectManagement\Models\NullProjectAttribute
+     * @group framework
+     */
+    public function testNull() : void
+    {
+        self::assertInstanceOf('\Modules\ProjectManagement\Models\ProjectAttribute', new NullProjectAttribute());
+    }
+
+    /**
+     * @covers Modules\ProjectManagement\Models\NullProjectAttribute
+     * @group framework
+     */
+    public function testId() : void
+    {
+        $null = new NullProjectAttribute(2);
+        self::assertEquals(2, $null->getId());
+    }
+
+    /**
+     * @covers Modules\ProjectManagement\Models\NullProjectAttribute
+     * @group framework
+     */
+    public function testJsonSerialize() : void
+    {
+        $null = new NullProjectAttribute(2);
+        self::assertEquals(['id' => 2], $null);
+    }
+}
diff --git a/tests/Models/NullProjectAttributeTypeTest.php b/tests/Models/NullProjectAttributeTypeTest.php
new file mode 100644
index 0000000..5b473b8
--- /dev/null
+++ b/tests/Models/NullProjectAttributeTypeTest.php
@@ -0,0 +1,52 @@
+<?php
+/**
+ * Jingga
+ *
+ * PHP Version 8.1
+ *
+ * @package   tests
+ * @copyright Dennis Eichhorn
+ * @license   OMS License 2.0
+ * @version   1.0.0
+ * @link      https://jingga.app
+ */
+declare(strict_types=1);
+
+namespace Modules\ProjectManagement\tests\Models;
+
+use Modules\ProjectManagement\Models\NullProjectAttributeType;
+
+/**
+ * @internal
+ */
+final class NullProjectAttributeTypeTest extends \PHPUnit\Framework\TestCase
+{
+    /**
+     * @covers Modules\ProjectManagement\Models\NullProjectAttributeType
+     * @group framework
+     */
+    public function testNull() : void
+    {
+        self::assertInstanceOf('\Modules\ProjectManagement\Models\ProjectAttributeType', new NullProjectAttributeType());
+    }
+
+    /**
+     * @covers Modules\ProjectManagement\Models\NullProjectAttributeType
+     * @group framework
+     */
+    public function testId() : void
+    {
+        $null = new NullProjectAttributeType(2);
+        self::assertEquals(2, $null->getId());
+    }
+
+    /**
+     * @covers Modules\ProjectManagement\Models\NullProjectAttributeType
+     * @group framework
+     */
+    public function testJsonSerialize() : void
+    {
+        $null = new NullProjectAttributeType(2);
+        self::assertEquals(['id' => 2], $null);
+    }
+}
diff --git a/tests/Models/NullProjectAttributeValueTest.php b/tests/Models/NullProjectAttributeValueTest.php
new file mode 100644
index 0000000..0b0d114
--- /dev/null
+++ b/tests/Models/NullProjectAttributeValueTest.php
@@ -0,0 +1,52 @@
+<?php
+/**
+ * Jingga
+ *
+ * PHP Version 8.1
+ *
+ * @package   tests
+ * @copyright Dennis Eichhorn
+ * @license   OMS License 2.0
+ * @version   1.0.0
+ * @link      https://jingga.app
+ */
+declare(strict_types=1);
+
+namespace Modules\ProjectManagement\tests\Models;
+
+use Modules\ProjectManagement\Models\NullProjectAttributeValue;
+
+/**
+ * @internal
+ */
+final class NullProjectAttributeValueTest extends \PHPUnit\Framework\TestCase
+{
+    /**
+     * @covers Modules\ProjectManagement\Models\NullProjectAttributeValue
+     * @group framework
+     */
+    public function testNull() : void
+    {
+        self::assertInstanceOf('\Modules\ProjectManagement\Models\ProjectAttributeValue', new NullProjectAttributeValue());
+    }
+
+    /**
+     * @covers Modules\ProjectManagement\Models\NullProjectAttributeValue
+     * @group framework
+     */
+    public function testId() : void
+    {
+        $null = new NullProjectAttributeValue(2);
+        self::assertEquals(2, $null->getId());
+    }
+
+    /**
+     * @covers Modules\ProjectManagement\Models\NullProjectAttributeValue
+     * @group framework
+     */
+    public function testJsonSerialize() : void
+    {
+        $null = new NullProjectAttributeValue(2);
+        self::assertEquals(['id' => 2], $null);
+    }
+}