Testing RSVP.Promises

[mixonic]

Howdy! In writing some tests for code using https://github.com/tildeio/rsvp.js, we've run into unexpected behavior. The fulfilled assertion helper is always passing, regardless of if the promise is actually rejected.

Promises in RSVP are deferred in different ways depending on your env. In Node, they are deferred with nextTick. In Firefox and Webkit with MutationObserver and a disconnected DOM node. In all other envs with setTimeout. See https://github.com/tildeio/rsvp.js/blob/master/lib/rsvp.js#L3 for detail.

This deferral means sinon's normal fake timers don't force the code to be synchronous. I was hoping this is the problem chai-as-promised was addressing. Here is a fiddle of chai-as-promised allowing an assertion that should be false:

http://jsfiddle.net/TqA5R/9/

[domenic]

No, Chai as Promised does not try to make promises fake-synchronous. If you want to expand the featureset of Sinon.JS to support different methods of fake-sync, feel free to file a bug there. It is not in scope for Chai as Promised.

If you don't try to hide the asynchronicity in your tests, you can either test using the notify helper:

chai.expect(this.promise).to.be.fulfilled.notify(done);

or using Mocha as Promised.

[mixonic]

Righto! This is behaving as expected http://jsfiddle.net/TqA5R/11/

    it("EXPECTED TO FAIL! should not be fulfilled on reject", function(done) {
        this.promise.reject();
        chai.expect(this.promise).to.be.fulfilled.notify(done);
    });
    it("should be fulfilled on resolve", function(done) {
        this.promise.resolve();
        chai.expect(this.promise).to.be.fulfilled.notify(done);
    });

The expected to fail fails. Thanks for the tip @domenic !

[domenic]

Glad to help! BTW I'm pretty sure the "done invoked with non-Error" is JSFiddle specific, since they use iframes and so instanceof Error fails cross-frame.