diff --git a/tests/phpunit/Unit/api/KnowledgeGraphApiLoadCategoriesTest.php b/tests/phpunit/Unit/api/KnowledgeGraphApiLoadCategoriesTest.php
index 96b9b3e..c92bb31 100644
--- a/tests/phpunit/Unit/api/KnowledgeGraphApiLoadCategoriesTest.php
+++ b/tests/phpunit/Unit/api/KnowledgeGraphApiLoadCategoriesTest.php
@@ -8,7 +8,7 @@ class KnowledgeGraphApiLoadCategoriesTest extends TestCase {
 	 * @covers KnowledgeGraphApiLoadCategories::getExamplesMessages
 	 */
 	public function testGetExamples() {
-		$instance = new KnowledgeGraphApiLoadCategories( new ApiMain(), null );
+		$instance = new KnowledgeGraphApiLoadCategories( new ApiMain(), '' );
 		$messages = $instance->getExamplesMessages();
 		$this->assertCount( 1, $messages );
 	}
diff --git a/tests/phpunit/Unit/api/KnowledgeGraphApiLoadNodesTest.php b/tests/phpunit/Unit/api/KnowledgeGraphApiLoadNodesTest.php
index 6120588..8cb610e 100644
--- a/tests/phpunit/Unit/api/KnowledgeGraphApiLoadNodesTest.php
+++ b/tests/phpunit/Unit/api/KnowledgeGraphApiLoadNodesTest.php
@@ -8,7 +8,7 @@ class KnowledgeGraphApiLoadNodesTest extends TestCase {
 	 * @covers KnowledgeGraphApiLoadNodes::getExamplesMessages
 	 */
 	public function testGetExamples() {
-		$instance = new KnowledgeGraphApiLoadNodes( new ApiMain(), null );
+		$instance = new KnowledgeGraphApiLoadNodes( new ApiMain(), '' );
 		$messages = $instance->getExamplesMessages();
 		$this->assertCount( 1, $messages );
 	}
diff --git a/tests/phpunit/Unit/api/KnowledgeGraphApiLoadPropertiesTest.php b/tests/phpunit/Unit/api/KnowledgeGraphApiLoadPropertiesTest.php
index 775dccd..4e68a6d 100644
--- a/tests/phpunit/Unit/api/KnowledgeGraphApiLoadPropertiesTest.php
+++ b/tests/phpunit/Unit/api/KnowledgeGraphApiLoadPropertiesTest.php
@@ -8,7 +8,7 @@ class KnowledgeGraphApiLoadPropertiesTest extends TestCase {
 	 * @covers KnowledgeGraphApiLoadProperties::getExamplesMessages
 	 */
 	public function testGetExamples() {
-		$instance = new KnowledgeGraphApiLoadProperties( new ApiMain(), null );
+		$instance = new KnowledgeGraphApiLoadProperties( new ApiMain(), '' );
 		$messages = $instance->getExamplesMessages();
 		$this->assertCount( 1, $messages );
 	}