How to create a unit test for a class which uses a trait?

Question

Simple as this:

class A {
  use StringTranslationTrait;
  
  public function something() {
    $b = 1+2;
    $this->t($b);
    return $b;
  }
}

I would like to unit test the something() method, but I can't since the StringTranslation trait uses a static container call:

Drupal\Core\DependencyInjection\ContainerNotInitializedException: \Drupal::$containe is not initialized yet. \Drupal::setContainer() must be called with a real container.

What do you suggest?

Answer 1

StringTranslationTrait also has a setStringTranslation() method so you can inject a string translation mock for exactly that purpose.

Answer 2

Following on Bedir's answer, here is an example.

I have a test that is using the class DurationService. DurationService uses the StringTranslationTrait as follows:

class DurationService implements DurationServiceInterface {
  use StringTranslationTrait;
  ...

To test this, I am doing the following (note, using a class that extends UnitTestCase):

$duration_service = new DurationService();
$duration_service->setStringTranslation($this->getStringTranslationStub());

This calls StringTranslationTrait::setStringTranslation() passing it the response from UnitTestCase::getStringTranslationStub().

Answer 3

Here is how I solved it, note your test must extend Drupal\Tests\UnitTestCase:

  /**
   * {@inheritdoc}
   */
  public function setUp() {
    parent::setUp();
    $container = new ContainerBuilder();
    \Drupal::setContainer($container);
    $container->set('string_translation', self::getStringTranslationStub());
  }

Answer 4

By implementing the ContainerFactoryPluginInterface you can use dependency injection to fake the string translation service.

class A implements ContainerFactoryPluginInterface { 
  use StringTranslationTrait; 

  public function __construct(array $configuration, $plugin_id, $plugin_definition) {
    parent::__construct($configuration, $plugin_id, $plugin_definition, TranslationInterface $string_translation);
    $this->stringTranslation =$string_translation;
  }

  public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
    return new static($configuration, $plugin_id, $plugin_definition, $container->get('string_translation'));
  }

  public function something() { 
    $b = 1+2; 
    $this->t($b); 
    return $b; 
  } 
}

Answer 5

Just take a look at the FormValidatorTest:

For the class

/**
 * Provides validation of form submissions.
 */
class FormValidator implements FormValidatorInterface {

  use StringTranslationTrait;

  public function __construct(RequestStack $request_stack, TranslationInterface $string_translation, CsrfTokenGenerator $csrf_token, LoggerInterface $logger, FormErrorHandlerInterface $form_error_handler) {
    $this->requestStack = $request_stack;
    $this->stringTranslation = $string_translation;
    $this->csrfToken = $csrf_token;
    $this->logger = $logger;
    $this->formErrorHandler = $form_error_handler;
  }

This is the test

  /**
   * Tests the 'validation_complete' $form_state flag.
   *
   * @covers ::validateForm
   * @covers ::finalizeValidation
   */
  public function testValidationComplete() {
    $form_validator = $this->getMockBuilder('Drupal\Core\Form\FormValidator')
      ->setConstructorArgs([new RequestStack(), $this->getStringTranslationStub(), $this->csrfToken, $this->logger, $this->formErrorHandler])
      ->setMethods(NULL)
      ->getMock();

    $form = [];
    $form_state = new FormState();
    $this->assertFalse($form_state->isValidationComplete());
    $form_validator->validateForm('test_form_id', $form, $form_state);
    $this->assertTrue($form_state->isValidationComplete());
  }

You can use as constructor param $this->getStringTranslationStub()