Added testutil.CollectAndCount

[bwplotka]

👋

I would like to propose additional function to testutil.go which will count metrics in a given Collector. The example usage can be seen here: https://github.com/thanos-io/thanos/blob/d758432436718ff6cd0d9136bc53653f4ec5cf47/pkg/compact/compact_e2e_test.go#L179

I also read the package documentation and I think I can agree that mock would be preferred for all of those test assertions IF such mock would be ready to use somewhere AND it would be easy to inject those mocked counter, gauges etc. The latter might be even impossible given the *Vec metrics are not interfaces e.g:

func NewCounterVec(opts CounterOpts, labelNames []string) *CounterVec { 

Overall I think, with this small function testutil gives all you need to unit test your instrumentation without mocks, except maybe registering part, which is easier to mock.

Signed-off-by: Bartlomiej Plotka bwplotka@gmail.com

[beorn7]

I guess we can do this.

Note that vectors are planned to get "interfaced" in v2 to allow the mocking you'd need here.

Just some notes about naming and doc comments.

[bwplotka]

Thanks for speedy review @beorn7 - all applied.

Side note: With interfaces, mock might be doable indeed. Do you think we should host such a prepared mock as well in v2 then? I think it would be useful.

[beorn7]

Do you think we should host such a prepared mock as well in v2 then? I think it would be useful.

That's the plan, at least vaguely.