Introduce phase groups for features

[pierDipi]

This is a feature that might allow simplifying setting up tests to prevent starvation, for example, this one https://github.com/knative/eventing/pull/7911 while continuing to get the benefits of the parallel phases and avoiding having the error prone calls like eventshub.Install(subscriberName2, eventshub.StartReceiver)(ctx, t)

f.Group("install subscribers", func(f *Feature) {
   f.Setup("install eventshub", eventshub.Install(subscriberName1, eventshub.StartReceiver))
})

f.Group("install brokers", func(f *Feature) {
   f.Setup("install broker1", broker.Install(...))
   f.Setup("install broker2", broker.Install(...))
})

f.Group("ready brokers", func(f *Feature) {
   f.Requirement("ready broker1", broker.IsReady(...))
   f.Requirement("ready broker2", broker.IsReady(...))
   f.Assert("addressable broker1", broker.IsAddressable(...))
   f.Assert("addressable broker2", broker.IsAddressable(...))
})

f.Group("install triggers", func(f *Feature) {
   f.Setup("install trigger1", trigger.Install(...))
   f.Setup("install trigger2", trigger.Install(...))
})

f.Group("ready triggers", func(f *Feature) {
   f.Setup("ready trigger1", trigger.IsReady(...))
   f.Setup("ready trigger2", trigger.IsReady(...))
})

f.Assert(...)

See also usage example in test/e2e/environment_test.go

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[mgencur]

I think it looks good. I will just give some time for any other reviewers. The only concern I have is that we already hold a slice of Features inside FeatureSet. I think FeatureSets could be used for this purpose as well like this:

        e := feature.NewFeatureNamed("install eventshub")
    e.Setup("install eventshub", eventshub.Install(subscriberName1, eventshub.StartReceiver))

    b := feature.NewFeatureNamed("install brokers")
    b.Setup("install broker1", broker.Install(...))
    b.Setup("install broker2", broker.Install(...))

    r := feature.NewFeatureNamed("ready brokers")
    r.Requirement("ready broker1", broker.IsReady(...))
    r.Requirement("ready broker2", broker.IsReady(...))
    r.Assert("addressable broker1", broker.IsAddressable(...))
    r.Assert("addressable broker2", broker.IsAddressable(...))

    it := feature.NewFeatureNamed("install triggers")
    it.Setup("install trigger1", trigger.Install(...))
    it.Setup("install trigger2", trigger.Install(...))

    rt := feature.NewFeatureNamed("ready triggers")
    rt.Setup("ready trigger1", trigger.IsReady(...))
    rt.Setup("ready trigger2", trigger.IsReady(...))

    a := feature.NewFeatureNamed("assert feature set")
    a.Assert(...)

    fs := &feature.FeatureSet{
        Name: "Multiple Brokers",
        Features: []*feature.Feature{
            e, b, r, it, rt, a,
        },
    }

    env.TestSet(ctx, t, fs)

Individual features are tested sequentially. The fact that we install/configure multiple features like Brokers, Triggers, etc. it makes sense to use FeatureSet, IMO.

[mgencur]

The other option (aside from using sub-features) would be something like this. Enforcing sequential execution of actions within a step, without compromising readability. Just putting it here for completeness: Additional type:

        type StepFnSequence struct {
        stepFunctions []StepFn
    }

    func (s *StepFnSequence) Add(fn StepFn) {
        s.stepFunctions = append(s.stepFunctions, fn)
    }

    func (s *StepFnSequence) Run(ctx context.Context, t T) {
        for _, fn := range s.stepFunctions {
            fn(ctx, t)
        }
    }

Actual usage:

    counterSeq := feature.StepFnSequence{}

    counterSeq.Add(eventshub.Install(subscriberName1, eventshub.StartReceiver))
    counterSeq.Add(broker.Install(...))

    feat.Setup("setup1", counterSeq.Run)

[mgencur]

/lgtm