causalityDuration Hides code execution in duration method

[v-zubko]

RxGo/duration.go

Line 84 in e94d354

func (d *causalityDuration) duration() time.Duration {

It is not expected that duration method will actually do such sophisticated thing. I expect it to return duration value only.

[teivah]

I disagree, it is expected. Actually, that's the purpose of it. Let's see why with a concrete example.

There's this BufferWithTime operator that batches the items at a given frequency. How would we implement unit tests for that? Most likely using a couple of time.Sleep(), right?

Now, let's see how the nominal test is implemented:

func Test_Observable_BufferWithTime(t *testing.T) {
	ctx, obs, d := timeCausality(1, 2, 3, tick, tick, 4, tick, 5, 6, 7, tick)
	obs = obs.BufferWithTime(d, WithContext(ctx))
	Assert(context.Background(), t, obs, HasItems(
		[]interface{}{1, 2, 3},
		[]interface{}{4},
		[]interface{}{5, 6, 7},
	))
}

Using timeCausality() that returns an Observable, we can configure whenever the timer is going to be triggered. This creates a deterministic unit test without any single time.Sleep().

If you need a simple mock, you can use mockDuration.

[v-zubko]

I understand why it is there and how it works. My point is that it is not obvious and may confuse others.
As to example with test it could be like this:

buf := <-Interval(WithDuration(time.Second), WithContext(ctx)).BufferWithTime(3 * time.Second, WithContext(ctx)).Observe()
assert.Len(t, buf, 3)

[v-zubko]

Another thing is that introducing artificial pauses while sending data will hide things like this #234

[teivah]

Let's keep only #234