diff --git a/tests/Models/NullQAAnswerTest.php b/tests/Models/NullQAAnswerTest.php
index f40661a..a2172b7 100755
--- a/tests/Models/NullQAAnswerTest.php
+++ b/tests/Models/NullQAAnswerTest.php
@@ -47,6 +47,6 @@ final class NullQAAnswerTest extends \PHPUnit\Framework\TestCase
     public function testJsonSerialize() : void
     {
         $null = new NullQAAnswer(2);
-        self::assertEquals(['id' => 2], $null);
+        self::assertEquals(['id' => 2], $null->jsonSerialize());
     }
 }
diff --git a/tests/Models/NullQAAnswerVoteTest.php b/tests/Models/NullQAAnswerVoteTest.php
index 35e1923..19e42b4 100755
--- a/tests/Models/NullQAAnswerVoteTest.php
+++ b/tests/Models/NullQAAnswerVoteTest.php
@@ -47,6 +47,6 @@ final class NullQAAnswerVoteTest extends \PHPUnit\Framework\TestCase
     public function testJsonSerialize() : void
     {
         $null = new NullQAAnswerVote(2);
-        self::assertEquals(['id' => 2], $null);
+        self::assertEquals(['id' => 2], $null->jsonSerialize());
     }
 }
diff --git a/tests/Models/NullQAAppTest.php b/tests/Models/NullQAAppTest.php
index 33febf2..404453f 100755
--- a/tests/Models/NullQAAppTest.php
+++ b/tests/Models/NullQAAppTest.php
@@ -47,6 +47,6 @@ final class NullQAAppTest extends \PHPUnit\Framework\TestCase
     public function testJsonSerialize() : void
     {
         $null = new NullQAApp(2);
-        self::assertEquals(['id' => 2], $null);
+        self::assertEquals(['id' => 2], $null->jsonSerialize());
     }
 }
diff --git a/tests/Models/NullQAQuestionTest.php b/tests/Models/NullQAQuestionTest.php
index b70234f..d8d8189 100755
--- a/tests/Models/NullQAQuestionTest.php
+++ b/tests/Models/NullQAQuestionTest.php
@@ -47,6 +47,6 @@ final class NullQAQuestionTest extends \PHPUnit\Framework\TestCase
     public function testJsonSerialize() : void
     {
         $null = new NullQAQuestion(2);
-        self::assertEquals(['id' => 2], $null);
+        self::assertEquals(['id' => 2], $null->jsonSerialize());
     }
 }
diff --git a/tests/Models/NullQAQuestionVoteTest.php b/tests/Models/NullQAQuestionVoteTest.php
index f4559e9..0220c28 100755
--- a/tests/Models/NullQAQuestionVoteTest.php
+++ b/tests/Models/NullQAQuestionVoteTest.php
@@ -47,6 +47,6 @@ final class NullQAQuestionVoteTest extends \PHPUnit\Framework\TestCase
     public function testJsonSerialize() : void
     {
         $null = new NullQAQuestionVote(2);
-        self::assertEquals(['id' => 2], $null);
+        self::assertEquals(['id' => 2], $null->jsonSerialize());
     }
 }