How to Test the Interaction of several Clients

If you need to simulate an interaction between different clients (think of a chat for instance), create several clients:

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        // ...
use Symfony\Component\HttpFoundation\Response;

$harry = static::createClient();

// before creating another client, shut down the current kernel first;
// this does NOT invalidate the $harry client, which can still be used after this call
self::ensureKernelShutdown();

$sally = static::createClient();

$harry->request('POST', '/say/sally/Hello');
$sally->request('GET', '/messages');

$this->assertEquals(Response::HTTP_CREATED, $harry->getResponse()->getStatusCode());
$this->assertRegExp('/Hello/', $sally->getResponse()->getContent());
    

Each call to createClient() boots a kernel and stores it as the current kernel for the test case. Creating another client while a kernel is still running triggers a LogicException. Call self::ensureKernelShutdown() before creating the next client.

Shutting down the kernel does not make previously created clients unusable. Existing clients (like $harry in the above example) can still perform requests after the call, but the next createClient() call will boot a fresh kernel instance.

This works except when your code maintains a global state or if it depends on a third-party library that has some kind of global state. In such a case, you can insulate your clients:

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        // ...
use Symfony\Component\HttpFoundation\Response;

$harry = static::createClient();
self::ensureKernelShutdown();
$sally = static::createClient();

$harry->insulate();
$sally->insulate();

$harry->request('POST', '/say/sally/Hello');
$sally->request('GET', '/messages');

$this->assertEquals(Response::HTTP_CREATED, $harry->getResponse()->getStatusCode());
$this->assertRegExp('/Hello/', $sally->getResponse()->getContent());
    

Insulated clients transparently run their requests in a dedicated and clean PHP process, thus avoiding any side effects.

Tip

As an insulated client is slower, you can keep one client in the main process, and insulate the other ones.

Warning

Insulating tests requires some serializing and unserializing operations. If your test includes data that can't be serialized, such as file streams when using the UploadedFile class, you'll see an exception about "serialization is not allowed". This is a technical limitation of PHP, so the only solution is to disable insulation for those tests.

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.

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