Add test cases for null models

tests/Models/NullQAAnswerTest.php

@@ -39,4 +39,14 @@ final class NullQAAnswerTest extends \PHPUnit\Framework\TestCase
         $null = new NullQAAnswer(2);
         self::assertEquals(2, $null->id);
     }
+
+    /**
+     * @covers Modules\QA\Models\NullQAAnswer
+     * @group module
+     */
+    public function testJsonSerialize() : void
+    {
+        $null = new NullQAAnswer(2);
+        self::assertEquals(['id' => 2], $null);
+    }
 }

tests/Models/NullQAAnswerVoteTest.php

@@ -39,4 +39,14 @@ final class NullQAAnswerVoteTest extends \PHPUnit\Framework\TestCase
         $null = new NullQAAnswerVote(2);
         self::assertEquals(2, $null->id);
     }
+
+    /**
+     * @covers Modules\QA\Models\NullQAAnswerVote
+     * @group module
+     */
+    public function testJsonSerialize() : void
+    {
+        $null = new NullQAAnswerVote(2);
+        self::assertEquals(['id' => 2], $null);
+    }
 }

tests/Models/NullQAAppTest.php

@@ -39,4 +39,14 @@ final class NullQAAppTest extends \PHPUnit\Framework\TestCase
         $null = new NullQAApp(2);
         self::assertEquals(2, $null->id);
     }
+
+    /**
+     * @covers Modules\QA\Models\NullQAApp
+     * @group module
+     */
+    public function testJsonSerialize() : void
+    {
+        $null = new NullQAApp(2);
+        self::assertEquals(['id' => 2], $null);
+    }
 }

tests/Models/NullQAQuestionTest.php

@@ -39,4 +39,14 @@ final class NullQAQuestionTest extends \PHPUnit\Framework\TestCase
         $null = new NullQAQuestion(2);
         self::assertEquals(2, $null->id);
     }
+
+    /**
+     * @covers Modules\QA\Models\NullQAQuestion
+     * @group module
+     */
+    public function testJsonSerialize() : void
+    {
+        $null = new NullQAQuestion(2);
+        self::assertEquals(['id' => 2], $null);
+    }
 }

tests/Models/NullQAQuestionVoteTest.php

@@ -39,4 +39,14 @@ final class NullQAQuestionVoteTest extends \PHPUnit\Framework\TestCase
         $null = new NullQAQuestionVote(2);
         self::assertEquals(2, $null->id);
     }
+
+    /**
+     * @covers Modules\QA\Models\NullQAQuestionVote
+     * @group module
+     */
+    public function testJsonSerialize() : void
+    {
+        $null = new NullQAQuestionVote(2);
+        self::assertEquals(['id' => 2], $null);
+    }
 }