How to lock private property in phpunit class?

Question

PHPUnit

Help the people, even caught a dumbass, in general, there is a beginning of such a class

class Relay implements ConsumerInterface
{
    /**
     * @var MemcachedAdapter
     */
    private $memory;

    public function __construct()
    {
        $client = MemcachedAdapter::createConnection('memcached://localhost');
        $this->memory = new MemcachedAdapter($client, $namespace = '',$defaultLifetime = 0);

I need to write a test for it, for this I need to lock $this->memory
I know how to write a mock, but I don’t know how to replace it in a private property.
In short, how to replace $this->memory so that my mock is there?

Answer 1

Simulation of your object:

class Relay
{
    private $privateProperty;

    public function __construct()
    {
        $this->privateProperty = new \stdClass();
    }

    // метод, который работает с приватным свойством
    public function call()
    {
        return $this->privateProperty;
    }
}

Method 1: Native PhpUnit + Reflection API

use PHPUnit\Framework\TestCase;

class RelayTest extends TestCase
{
    public function testCall(): void
    {
        $reflectionClass = new \ReflectionClass(Relay::class);
        $reflectionProperty = $reflectionClass->getProperty('privateProperty');
        $reflectionProperty->setAccessible(true);

        // создаем наш объект БЕЗ конструктора
        $relay = $reflectionClass->newInstanceWithoutConstructor();

        // Меняем свойство и вызываем метод, работающий с этим приватным полем
        $reflectionProperty->setValue($relay, 1111);
        self::assertEquals(1111, $relay->call());

        // Меняем свойство и вызываем метод, работающий с этим приватным полем
        $reflectionProperty->setValue($relay, 'aaaa');
        self::assertEquals('aaaa', $relay->call());
    }
}

Method 2: Via Codeception Stub

class RelayTest extends TestCase
    public function testCall(): void
    {
        /** @var Example $stub */
        $stub = Stub::make(Relay::class, [
            'privateProperty' => 1111,
        ]);
        self::assertEquals(1111, $stub->call());

        $stub = Stub::make(Relay::class, [
            'privateProperty' => 'aaaa',
        ]);
        self::assertEquals('aaaa', $stub->call());
    }
}

Digressions and useful tips:

• For some reason, the standard, long-used by me, method with the injection of a private field mock did not work and always returned null.
  
• Use the Inversion of Control Principle, such as constructor dependency injection or assignment method injection in the NullObject constructor. Both ways will be good for testing.