symfony 5 how to mock/replace service in container - symfony

Question

I want to make a mock for some class in my functional test. Let's say I want to mock some custom command bus realization.
First of all I need to register that service as a public in the services_test.yaml:
services:
_defaults:
public: true
App\CommandBus: ~
but still even if I did so I'm getting error service is already initialized, you cannot replace it when doing something like:
$commandBus = $this->createMock(CommandBus::class);
$commandBus->expects(self::once())
->method('dispatch')
->with($data)
->willReturn($response);
self::$container->set(CommandBus::class, $commandBus);
So how can I easily mock some object and insert mocked version to the container???
Probably I can make some wrapper for tests link it with interface in services_test.yaml, and add a methods like setExpectiotion which will chekc if expectation set and if so instead of running command return it. But it's extra work and it's taking a lot of time to design such a class for each service I want to mock.
Is there any other way to mock some service?? Thanks in advice!

Answer 1

I assume your command bus is using an asynchronous transport type. If you wish you can solve this problem using sync transport for tests instead. You don't need to mock it in this case, because if you will mock command bus, you will test mock instead of the whole process.
Let's create a new config in config/packages/test/messenger.yaml
framework:
messenger:
transports:
command_bus: 'sync://'
Then enable the functional test without worrying about the consumer.
If you want to debug container for tests, you can check it using command
./bin/console debug:container -e test
Please let me know if that solves your problem.