diff --git a/.gitignore b/.gitignore
index 7579f74..f0dcfe4 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 vendor
 composer.lock
+tests/.phpunit.result.cache
diff --git a/tests/AbstractTestCase.php b/tests/AbstractTestCase.php
index 66b90a8..740a723 100644
--- a/tests/AbstractTestCase.php
+++ b/tests/AbstractTestCase.php
@@ -22,7 +22,7 @@ protected function assertVastDocumentSameWithXmlFixture($expectedXmlFixturePath,
     {
         $this->assertXmlStringEqualsXmlFile(
             $this->getFullXMLFixturePath($expectedXmlFixturePath),
-            $actualXmlDomDocument->toDomDocument()
+            (string)$actualXmlDomDocument
         );
     }
 }
diff --git a/tests/DocumentTest.php b/tests/DocumentTest.php
index c4bcc3b..3c8a235 100644
--- a/tests/DocumentTest.php
+++ b/tests/DocumentTest.php
@@ -238,11 +238,10 @@ public function testCreateAdSectionWithDelivery()
 
     /**
      * Test for creating media file with invalid delivery
-     * @expectedException        \Exception
-     * @expectedExceptionMessage Wrong delivery specified
      */
     public function testCreateAdSectionWithInvalidDelivery()
     {
+        $this->expectExceptionMessage('Wrong delivery specified');
         $factory = new Factory();
         $document = $factory->create('2.0');
 
@@ -453,8 +452,8 @@ public function testToString()
         $factory = new Factory();
         $document = $factory->create('2.0');
 
-        $this->assertContains('<?xml version="1.0" encoding="UTF-8"?>', (string)$document);
-        $this->assertContains('<VAST version="2.0"/>', (string)$document);
+        $this->assertStringContainsString('<?xml version="1.0" encoding="UTF-8"?>', (string)$document);
+        $this->assertStringContainsString('<VAST version="2.0"/>', (string)$document);
     }
 
     /**