Fake hub to functionnal test

[renishv8]

Hello,

I try to use mercure in my functionnal tests, i followed the doc but it does not work. I'd like to have a fake class exactly like the doc suggests.
I use symfony 6.3, phpunit 9.5. I tried to configure the default class like this :

    mercure.hub.default:
        class: App\Tests\Functional\Stub\HubStub

I have this error

Symfony\Component\Config\Exception\LoaderLoadException : Container extension "mercure.hub.default" is not registered in /srv/config/packages/mercure.yaml (which is being imported from "/srv/src/Kernel.php").

The bundle works fine in development mode, it's well imported. In the bundles.php, it's all => true setted

I tried to use the default_hub but it's not working either.

Do you have any ideas or recommandations ?
Thanks :)