Functional Testing Events and Subscribers in Symfony 4 - php

Question

I need to functionally test the a subscriber in Symfony 4 and I'm having problems finding how. The Subscriber has the following structure
/**
* Class ItemSubscriber
*/
class ItemSubscriber implements EventSubscriberInterface
{
/**
* #var CommandBus
*/
protected $commandBus;
/**
* Subscriber constructor.
*
* #param CommandBus $commandBus
*/
public function __construct(CommandBus $commandBus)
{
$this->commandBus = $commandBus;
}
/**
* {#inheritdoc}
*/
public static function getSubscribedEvents()
{
return [
CommandFailedEvent::NAME => 'onCommandFailedEvent',
];
}
/**
* #param CommandFailedEvent $event
*
* #throws Exception
*/
public function onCommandFailedEvent(CommandFailedEvent $event)
{
$item = $event->getItem();
$this->processFailed($item);
}
/**
* Sends message
*
* #param array $item
*
* #throws Exception
*/
private function processFailed(array $item)
{
$this->commandBus->handle(new UpdateCommand($item));
}
}
The flow of the subscriber is receiving an internal event and send a message by rabbit through the command bus to another project.
How can I test that dispatching the event CommandFailedEvent the line in processFailed(array $item) is executed?
Does anyone has documentation on best practices to test Events and Subscribers in Symfony 4?

Answer 1

If you want to test the process of a command bus handler being call you could test dependency method calls thanks to mock expects. You have some examples in the PHPUnit documentation.
For instance, you would have something like:
$commandBus = $this->getMockBuilder(CommandBus::class)->disableOriginalConstructor()->getMock();
$commandBus->expects($this->once())->method('handle');
// Create your System Under Test
$SUT = new CommandFailedSubscriber($commandBus);
// Create event
$item = $this->getMockBuilder(YourItem::class)->getMock();
$event = new CommandFailedEvent($item);
// Dispatch your event
$dispatcher = new EventDispatcher();
$dispatcher->addSubscriber($SUT);
$dispatcher->dispatch($event);
I hope this would be enough for you to explore possibilities and to have the coverage needed for your feature.
Have a nice time testing!