Testing Symfony constraint validators with PHPUnit

declare(strict_types=1);

namespace AppBundle\Validator\Constraint\Registration;

use AppBundle\Repository\RegistrationRepositoryInterface;
use Symfony\Component\Validator\Constraint;
use Symfony\Component\Validator\ConstraintValidator;

class EmailValidator extends ConstraintValidator
{
    private $registrationRepository;

    public function __construct(
        RegistrationRepositoryInterface $registrationRepository
    ) {
        $this->registrationRepository = $registrationRepository;
    }

    public function validate($value, Constraint $constraint): void
    {
        if (!empty($this->registrationRepository->findByEmail($value))) {
            $this->context->buildViolation('The email address has already been used.')->addViolation();
        }   
    }
}

declare(strict_types=1);

namespace Tests\AppBundle\Validator\Constraint\Registration;

use AppBundle\Repository\RegistrationRepositoryInterface;
use AppBundle\Validator\Constraint\Registration\EmailValidator;
use PHPUnit\Framework\TestCase;
use PHPUnit_Framework_MockObject_MockObject;
use Symfony\Component\Validator\Constraint;
use Symfony\Component\Validator\Context\ExecutionContextInterface;
use Symfony\Component\Validator\Violation\ConstraintViolationBuilderInterface;
use Tests\DataFixtures\Entity\RegistrationData;

class EmailValidatorTest extends TestCase
{
    /** @var RegistrationRepositoryInterface|PHPUnit_Framework_MockObject_MockObject */
    private $registrationRepositoryMock;
    /** @var EmailValidator */
    private $emailValidator;

    protected function setUp()
    {
        $this->registrationRepositoryMock = $this->getMockBuilder(RegistrationRepositoryInterface::class)
            ->disableOriginalConstructor()
            ->getMock();

        $this->emailValidator = new EmailValidator($this->registrationRepositoryMock);
    }

    /**
     * @test
     */
    public function validate_builds_violation_if_registration_object_already_exists()
    {
        $value = 'email_goes_here';
        $registrationEntity = RegistrationData::get();

        $this->registrationRepositoryMock
            ->expects($this->once())
            ->method('findByEmail')
            ->willReturn([$registrationEntity]);

        /** @var ExecutionContextInterface|PHPUnit_Framework_MockObject_MockObject $executionContextMock */
        $executionContextMock = $this->getMockBuilder(ExecutionContextInterface::class)
            ->disableOriginalConstructor()
            ->getMock();

        /** @var ConstraintViolationBuilderInterface|PHPUnit_Framework_MockObject_MockObject $executionContextMock */
        $constraintViolationBuilderMock = $this->getMockBuilder(ConstraintViolationBuilderInterface::class)
            ->disableOriginalConstructor()
            ->getMock();

        $executionContextMock
            ->expects($this->once())
            ->method('buildViolation')
            ->with('The email address has already been used.')
            ->willReturn($constraintViolationBuilderMock);

        $constraintViolationBuilderMock
            ->expects($this->once())
            ->method('addViolation')
            ->willReturn(null);

        /** @var Constraint|PHPUnit_Framework_MockObject_MockObject $constraintMock */
        $constraintMock = $this->getMockBuilder(Constraint::class)
            ->disableOriginalConstructor()
            ->getMock();

        $this->emailValidator->initialize($executionContextMock);
        $this->emailValidator->validate($value, $constraintMock);
    }
}

$ vendor/bin/phpunit --filter EmailValidatorTest tests/AppBundle/Validator/Constraint/Registration/EmailValidatorTest.php
PHPUnit 6.3.1 by Sebastian Bergmann and contributors.

.                                                                   1 / 1 (100%)

Time: 80 ms, Memory: 6.00MB

OK (1 test, 3 assertions)