[FrameworkBundle] Allow setting private services with the test container

[nicolas-grekas]

Q	A
Branch?	6.3
Bug fix?	no
New feature?	yes
Deprecations?	no
Tickets	-
License	MIT
Doc PR	-

This PR allows mocking a service for a test case. A typical example could be for HttpClient:

static::getContainer()->set('example.client', new MockHttpClient(...));

// do stuff that will use `example.client` and will get mock responses instead of using the network

[damienalexandre]

Really looking forward this one! Thanks a lot!

[bastnic]

Awesome!

[Seldaek]

Is this cool? Yes I think so. It'd make tests less brittle if you don't have to instantiate smth but can rely on auto wiring too.

Just one thought: could it detect if a service which was set is then not used during a test and output a warning? That'd allow to catch errors where you configure stuff that's useless / dead code. Possibly would back fire tho and be more annoying than useful :)

[nicolas-grekas]

@Seldaek that'd be neat but I don't know how we could make that work. There is no infrastructure in the container to know when a service is injected into another one, and even less to know when such a service is actually used.

On a case by case basis, it's doable of course:

$client = new TraceableHttpClient(new MockHttpClient(...));
static::getContainer()->set('example.client', $client);

// do stuff

// do expectations using TraceableHttpClient's API

[tgalopin]

This would also be super useful to mock the clock (I do it all the time, mocking in the config isn't enough to test all cases):

static::getContainer()->set(ClockInterface::class, new MockClock('2022-11-23 00:00:00', 'UTC'));

[nicolas-grekas]

@tgalopin see also #48642
TL;DR, use ClockSensitiveTrait::mockTime().

[dunglas]

Awesome!

[fabpot]

Thank you @nicolas-grekas.

[Bilge]

1. How does this work given the container has already been compiled and, where such services are replaced, the object they are replacing has already been injected into dependents and thus will not see the effect of this replacement?
2. For @nicolas-grekas specifically, seeing as this PR is at odds with your original assessment, what changed?

[stof]

@Bilge you must do the injection before services are instantiated.
Compiling a container is not when instantiation happens.

[stof]

And the special TestContainer allowing you to retrieve private services already has a restriction that this does not support inlined services. This injection has the same restriction.