[angular.js] Jasmine tests with $q

[Pawel Kozlowski]

Hi!

I'm having trouble making a basic test working with $q promisses:
http://jsfiddle.net/pkozlowski_opensource/Ls8eW/2/
Does anyone have an idea about what is going on here?

The funny thing is that (almost) the same use case works OK when
executed in angular, without Jasmine:
http://jsfiddle.net/pkozlowski_opensource/kjtbb/

I guess I'm missing sth that is obvious but somehow just can't
understand what is going on here....

Cheers,
Pawel

[Witold Szczerba]

Hi,
take a look at the source code:
https://github.com/angular/angular.js/blob/master/src/ng/q.js

The 'resolve' function does not execute immediately, it schedules
execution using $rootScope.$evalAsync, so you are asserting on a
result too early.

Take a look at the example you have provided:
http://jsfiddle.net/pkozlowski_opensource/kjtbb/
You said it is the funny thing that the example works OK without
Jasmine, but it actually works exactly the same. Look at this:
http://jsfiddle.net/witoldsz/kjtbb/1/

The only thing is: how to defer the assertion in Jasmine...

Regards,
Witold Szczerba

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[Witold Szczerba]

Hi again,
here is working code:
http://jsfiddle.net/witoldsz/Ls8eW/4/

As I wrote above, $q uses root scope's $evalAsync to schedule
execution. The only thing I do not get is why does it work only when I
explicitly call $digest on root scope... (last line before final
assert).
Can someone explain, please? The source code of $digest is a little
bit complicated and right now I have nothing but a web browser to read
and analyze it...

The final thought is: should developers be aware that $q delegates to
rootScope.$evalAsync? Isn't that an implementation detail? Maybe it
would be a good idea to add a 'flush' method to $q or deffered objects
in testing environment?

Regards,
Witold Szczerba

[Pawel Kozlowski]

Hi Witold!

Thnx so much for taking time looking into this. I didn't realize that
'resolve' is called via root scope's $evalAsync, so I've learned
something here!
As often with async stuff it wasn't so obvious for me and I was even
persuaded that my example without Jasmine works in the synchronous
way... So in the end this is just timing issue with Jasmine. I wonder
if we need mock version of $q (with flush()) since calling $digest
will do the trick.

With this new insight I need to go back to the Bogdan's question that
trigger this $q + Jasmine questions for me:
https://groups.google.com/forum/?fromgroups#!topic/angular/N5yBJvl7Pbg

Once again, thnx for your help!

Cheers,
Pawe;

[Peter Bacon Darwin]

Hi Witold

I was just playing with this situation and your fiddle helps tremendously.

Regarding your question about explicitly calling $digest on root scope:

• According to this in the docs - http://docs.angularjs.org/guide/concepts - under the heading Runtime, you can see that evaluating the $evalAsync queue is part of the $digest loop.
  
• From looking at the src, there is a $evalAsync queue for each scope.
  
• Since $q pushes defers to the $rootScope's $evalAsync queue, that is where you have to run the $digest.

Equally, one could have simply called $apply on any scopeto get the same effect.

Pete

[ThomasBurleson]

@Pete, @Witold,

Last night I ran into this same issue build Jasmine/Karma tests on promised-based services (using Karma and RequireJS).  

Attached is a self-contained, documentd Gist sample: PeopleListControllerSpec.js

While I understand the issue, I think it reveals a bigger concern to me:

What if I had used Q.js or When.js as my Promise-library (instead of AngularJS built-in $q). 

Then I would not have encountered this issue. So the fact that $q works fundamentally different is very worrisome.

- Thomas

[ThomasBurleson]

I just saw that Igor Minar has a fix in his fork regarding this exact issue.

Should be in the AngularJS v1.2.x master soon....

[Jamie @GotNoSugarBaby]

Hi all,

I came across this quirk today and documented it on Stack Overflow at Testing immediately resolved $.defer() with Jasmine.

Thanks,

Jamie Mason / @fold_left