Add test for checking content type

Author: ssfinney

tests/MailTrackingTest.php

@@ -156,6 +156,19 @@ public function it_checks_email_cc_address()
         $this->assertEquals($this->mail_tracking, $this->callProtectedMethod('seeEmailCc', ['cc@domain.tld']));
     }
 
+    /**
+     * @test
+     * @group unit
+     */
+    public function it_checks_email_content_type()
+    {
+        $message = $this->makeMessage();
+        $message->setContentType('text/html');
+        $this->mail_tracking->recordMail($message);
+
+        $this->assertEquals($this->mail_tracking, $this->callProtectedMethod('seeEmailContentTypeEquals', ['text/html']));
+    }
+
     /**
      * @test
      * @group unit