How to test dependency injection with PHPUnit on symfony 4 - symfony

Question

In a symfony 4 project, many services/controllers need log.
Trying to use the advantage of traits & autowire options given by symfony, I created a loggerTrait that will be passed to the different services.
namespace App\Helper;
use Psr\Log\LoggerInterface;
use Psr\Log\LogLevel;
trait LoggerTrait
{
/** #var LoggerInterface */
private $logger;
/** #var array */
private $context = [];
/**
* #return LoggerInterface
*/
public function getLogger(): LoggerInterface
{
return $this->logger;
}
/**
* #required
*
* #param LoggerInterface|null $logger
*/
public function setLogger(?LoggerInterface $logger): void
{
$this->logger = $logger;
}
public function logDebug(string $message, array $context = []): void
{
$this->log(LogLevel::DEBUG, $message, $context);
}
...
}
(inspired by symfonycasts.com)
A service will be using this trait
namespace App\Service;
use App\Helper\LoggerTrait;
class BaseService
{
use LoggerTrait;
/** #var string */
private $name;
public function __construct(string $serviceName)
{
$this->name = $serviceName;
}
public function logName()
{
$this->logInfo('Name of the service', ['name' => $this->name]);
}
}
It works perfectly but I couldn't succeed to test it.
I tried to extend KernelTestCase in my test to mock an loggerInterface but I receive Symfony\Component\DependencyInjection\Exception\InvalidArgumentException: The "Psr\Log\LoggerInterface" service is private, you cannot replace it which make perfect sens.
Here my test:
namespace App\Tests\Service;
use App\Service\BaseService;
use Psr\Log\LoggerInterface;
use Symfony\Bundle\FrameworkBundle\Test\KernelTestCase;
class BaseServiceTest extends KernelTestCase
{
private function loggerMock()
{
return $this->createMock(LoggerInterface::class);
}
protected function setUp()
{
self::bootKernel();
}
/**
* #test
* #covers ::logName
*/
public function itShouldLogName()
{
// returns the real and unchanged service container
$container = self::$kernel->getContainer();
// gets the special container that allows fetching private services
$container = self::$container;
$loggerMock = $this->loggerMock();
$loggerMock->expect(self::once())
->method('log')
->with('info', 'Name of the service', ['name' => 'service_test']);
$this->logger = $container->set(LoggerInterface::class, $loggerMock);
$baseService = new BaseService('service_test');
var_dump($baseService->getLogger());
}
}
Is there a solution to test such a logger inside the service ?

Answer 1

You can override the service to be public (only for the test environment) in your config_test.yml as follows:
services:
Psr\Log\LoggerInterface:
public: true
This is commonly done for testing private services.