Unsubscribe from marble tests

[ktrott]

Can't do tests with the marble tests to show if someone wants to unsubscribe at some point: explicit disposable vs. completion. Need some way to tell the test scheduler to unsubscribe from the test observable at a particular frame.

[staltz]

While making tests for mergeMap I think I figured one potential way of making this happen.

---

The subscription is done in TestScheduler.expect():

    this.schedule(() => {
      observable.subscribe((value) => {
        actual.push({ frame: this.frame, notification: Notification.createNext(value) });
      }, (err) => {
        actual.push({ frame: this.frame, notification: Notification.createError(err) });
      }, () => {
        actual.push({ frame: this.frame, notification: Notification.createComplete() });
      });
    }, 0);

We need to keep that subscription inside expect(). We can change expect's signature to be

expect(observable: Observable<any>, unsubscriptionMarbles?: string)

So you can optionally provide a marble diagram for the unsubscription moment. And then use it like this:

var e1 = hot('--a-^---b--c----d-------e--f--g--|');
var expected =    '-----b--c----d---';
var unsub =  '----------------------|';

expectObservable(e1.delay(20), unsub).toBe(expected);

Notice the second parameter given to expectObservable.

What do you think? Does this solve also tricky use cases we had for switch/switchMap? I would know how to implement that above.

[benlesh]

That's not bad. But wouldn't the unsub marbles be:

var e1 = hot('--a-^---b--c----d-------e--f--g--|');
var expected =   '-----b--c----d---';
var unsub =      '----------------------|';

expectObservable(e1.delay(20), unsub).toBe(expected);

So that the ^ and first -'s are aligned?

[staltz]

Correct, was my mistake.

[benlesh]

@staltz, I like it, but I think the character should be different than |... maybe this is a good place for !, since it looks similar. That would also mean fewer changes and assertions in the code to parse the marbles and process them.

[staltz]

Ok, let's do exclamation then. Another character I considered was underscore, because it would look a bit like the opposite of ^. Subscribe is up ^, unsubscribe is down _.

var e1 = hot('--a-^---b--c----d-------e--f--g--|');
var expected =   '-----b--c----d---';
var unsub =      '----------------------_';

expectObservable(e1.delay(20), unsub).toBe(expected);

But I'm fine with exclamation:

var e1 = hot('--a-^---b--c----d-------e--f--g--|');
var expected =   '-----b--c----d---';
var unsub =      '----------------------!';

expectObservable(e1.delay(20), unsub).toBe(expected);

[staltz]

This issue can be closed since it's fully implemented.