$form_builder = $this->container->get('form_builder');
$form_builder->submitForm($this, $form_state);
$form_builder = $this->container->get('form_builder');
$form_builder->submitForm($this, $form_state);
$this->assertTrue(isset($messages['error']));
$error_messages = $messages['error'];
$this->assertEqual($error_messages[0], 'Three field is required.');
$this->assertTrue(isset($messages['error']));
$error_messages = $messages['error'];
$this->assertEqual($error_messages[0], 'Three field is required.');