Unit testing with Symfony's flashBag sessions - symfony

Question

I'm creating an application in Silex with unit tests.
Running unit tests works fine against the regular session handler:
$app->register(new Silex\Provider\SessionServiceProvider(), array(
'session.storage.options' => array(
'cookie_lifetime' => 1209600, // 2 weeks
),
));
and setting this flag in my unit tests:
$this->app['session.test'] = true;
If I don't set that session.test flag, my unit tests throw a headers already sent error and all fail. With it on, my tests run well.
The issue is I am attempting to use the flashBag feature (session info that lasts only until first request then get removed):
$foo = $app['session']->getFlashBag()->all();
The flashBag does not seem to respect the session.test flag, and attempts to send headers, which cause all my unit tests to fail:
24)
Yumilicious\UnitTests\Validator\PersonAccountTest::setConstraintsPassesWithMinimumAttributes
RuntimeException: Failed to start the session because headers have
already been sent.
/webroot/yumilicious/vendor/symfony/http-foundation/Symfony/Component/HttpFoundation/Session/Storage/NativeSessionStorage.php:142
/webroot/yumilicious/vendor/symfony/http-foundation/Symfony/Component/HttpFoundation/Session/Storage/NativeSessionStorage.php:262
/webroot/yumilicious/vendor/symfony/http-foundation/Symfony/Component/HttpFoundation/Session/Session.php:240
/webroot/yumilicious/vendor/symfony/http-foundation/Symfony/Component/HttpFoundation/Session/Session.php:250
/webroot/yumilicious/src/app.php:38
/webroot/yumilicious/tests/Yumilicious/UnitTests/Base.php:13
/webroot/yumilicious/vendor/silex/silex/src/Silex/WebTestCase.php:34
/webroot/yumilicious/vendor/EHER/PHPUnit/src/phpunit/phpunit.php:46
/webroot/yumilicious/vendor/EHER/PHPUnit/bin/phpunit:5
I've narrowed it down to this bit of code: https://github.com/symfony/symfony/blob/master/src/Symfony/Component/HttpFoundation/Session/Storage/NativeSessionStorage.php#L259
Specifically, line 262. Commenting out that single line allows my tests to work properly and all pass green.
I've searched quite a bit to get this to work, but am not having any luck. I think it's because the flashBag stuff is new (https://github.com/symfony/symfony/blob/master/src/Symfony/Component/HttpFoundation/Session/Session.php#L305) and the old methods are being deprecated.
Any suggestions on getting my unit tests to work would be awesome.

Answer 1

For testing you need to replace the session.storage service with an instance of MockArraySessionStorage:
use Symfony\Component\HttpFoundation\Session\Storage\MockArraySessionStorage;
$app['session.storage'] = new MockArraySessionStorage();
This is because the native one tries to send a cookie via header which of course fails in a test environment.
EDIT: There is now a session.test parameter that you should set to true. That will automatically make the session use a mock storage.

Answer 2

I had this happen too, if i am not mistaking i fixed by having my unittests run via a different environment, wich has
framework:
test: ~
session:
storage_id: session.storage.mock_file
set in the config_test.yml

Answer 3

I came across similar problem today and temp fix would be to comment out block of code in
\Symfony\Component\HttpFoundation\Session\Storage\NativeSessionStorage
in start() method
/*
if (ini_get('session.use_cookies') && headers_sent()) {
throw new \RuntimeException('Failed to start the session because headers have already been sent.');
}
*/
This solution keeps tests "green" and from looks of it the application session functionality as is.