diff --git a/tests/Models/NullKanbanBoardTest.php b/tests/Models/NullKanbanBoardTest.php
index 0a1d467..47305a3 100755
--- a/tests/Models/NullKanbanBoardTest.php
+++ b/tests/Models/NullKanbanBoardTest.php
@@ -23,7 +23,7 @@ final class NullKanbanBoardTest extends \PHPUnit\Framework\TestCase
 {
     /**
      * @covers Modules\Kanban\Models\NullKanbanBoard
-     * @group framework
+     * @group module
      */
     public function testNull() : void
     {
@@ -32,11 +32,21 @@ final class NullKanbanBoardTest extends \PHPUnit\Framework\TestCase
 
     /**
      * @covers Modules\Kanban\Models\NullKanbanBoard
-     * @group framework
+     * @group module
      */
     public function testId() : void
     {
         $null = new NullKanbanBoard(2);
         self::assertEquals(2, $null->id);
     }
+
+    /**
+     * @covers Modules\Kanban\Models\NullKanbanBoard
+     * @group module
+     */
+    public function testJsonSerialize() : void
+    {
+        $null = new NullKanbanBoard(2);
+        self::assertEquals(['id' => 2], $null);
+    }
 }
diff --git a/tests/Models/NullKanbanCardCommentTest.php b/tests/Models/NullKanbanCardCommentTest.php
index 671d783..f4e8ccd 100755
--- a/tests/Models/NullKanbanCardCommentTest.php
+++ b/tests/Models/NullKanbanCardCommentTest.php
@@ -23,7 +23,7 @@ final class NullKanbanCardCommentTest extends \PHPUnit\Framework\TestCase
 {
     /**
      * @covers Modules\Kanban\Models\NullKanbanCardComment
-     * @group framework
+     * @group module
      */
     public function testNull() : void
     {
@@ -32,11 +32,21 @@ final class NullKanbanCardCommentTest extends \PHPUnit\Framework\TestCase
 
     /**
      * @covers Modules\Kanban\Models\NullKanbanCardComment
-     * @group framework
+     * @group module
      */
     public function testId() : void
     {
         $null = new NullKanbanCardComment(2);
         self::assertEquals(2, $null->id);
     }
+
+    /**
+     * @covers Modules\Kanban\Models\NullKanbanCardComment
+     * @group module
+     */
+    public function testJsonSerialize() : void
+    {
+        $null = new NullKanbanCardComment(2);
+        self::assertEquals(['id' => 2], $null);
+    }
 }
diff --git a/tests/Models/NullKanbanCardTest.php b/tests/Models/NullKanbanCardTest.php
index d10134f..53165ff 100755
--- a/tests/Models/NullKanbanCardTest.php
+++ b/tests/Models/NullKanbanCardTest.php
@@ -23,7 +23,7 @@ final class NullKanbanCardTest extends \PHPUnit\Framework\TestCase
 {
     /**
      * @covers Modules\Kanban\Models\NullKanbanCard
-     * @group framework
+     * @group module
      */
     public function testNull() : void
     {
@@ -32,11 +32,21 @@ final class NullKanbanCardTest extends \PHPUnit\Framework\TestCase
 
     /**
      * @covers Modules\Kanban\Models\NullKanbanCard
-     * @group framework
+     * @group module
      */
     public function testId() : void
     {
         $null = new NullKanbanCard(2);
         self::assertEquals(2, $null->id);
     }
+
+    /**
+     * @covers Modules\Kanban\Models\NullKanbanCard
+     * @group module
+     */
+    public function testJsonSerialize() : void
+    {
+        $null = new NullKanbanCard(2);
+        self::assertEquals(['id' => 2], $null);
+    }
 }
diff --git a/tests/Models/NullKanbanColumnTest.php b/tests/Models/NullKanbanColumnTest.php
index a061f0f..9fd91f4 100755
--- a/tests/Models/NullKanbanColumnTest.php
+++ b/tests/Models/NullKanbanColumnTest.php
@@ -23,7 +23,7 @@ final class NullKanbanColumnTest extends \PHPUnit\Framework\TestCase
 {
     /**
      * @covers Modules\Kanban\Models\NullKanbanColumn
-     * @group framework
+     * @group module
      */
     public function testNull() : void
     {
@@ -32,11 +32,21 @@ final class NullKanbanColumnTest extends \PHPUnit\Framework\TestCase
 
     /**
      * @covers Modules\Kanban\Models\NullKanbanColumn
-     * @group framework
+     * @group module
      */
     public function testId() : void
     {
         $null = new NullKanbanColumn(2);
         self::assertEquals(2, $null->id);
     }
+
+    /**
+     * @covers Modules\Kanban\Models\NullKanbanColumn
+     * @group module
+     */
+    public function testJsonSerialize() : void
+    {
+        $null = new NullKanbanColumn(2);
+        self::assertEquals(['id' => 2], $null);
+    }
 }