feat(ngMock): add flushByIndex function

[atogata]

Request Type: feature

How to reproduce:

Component(s): ngMock

Impact: small

Complexity: small

This issue is related to:

Detailed Description:

I've recently needed to flush httpBackend requests in an arbitrary order to add unit tests around an edge case. This PR satisfies that need.

Other Comments:

Adds a flushByIndex function to allow pending requests on httpBackend to be flushed in an arbitrary
order.

[mary-poppins]

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• Uses the issue template (#6412)

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[atogata]

Updated with the issue template

[pkozlowski-opensource]

@atogata currently the TravisCI build is failing (https://travis-ci.org/angular/angular.js/jobs/19426249) so this PR needs more work.

But besides the build issues I would love to know more about your actual use-case. If I'm not mistaken request are flushed in the order of expectations set so you can control the order by registering expectations. Could you provide an example unit test that is easier to write with the index-based flushing?

[atogata]

@pkozlowski-opensource Thank you for your response, the exact use case depends highly on some specifics of the system I’m working with, but I will try to explain as clearly as possible.

We have a system that can be called in a manner like:
service.get(‘/events’) called at T=0s
service.get(‘/events/eventKeyA’) called at T=2s

The /events endpoint will always return the result of /events/eventKeyA, along with other entities. Since both endpoints can be slow, we have some logic in place such that service.get(‘/events/eventKeyA’) can return data as soon as it’s available from the /events call and not have to wait for the singular call.

The problem in testing this seems to be that

httpBackend.expectGET(‘/v1.0/events’);
httpBackend.expectGET(‘/v1.0/events/eventKeyA’);
service.get(‘/events’);
service.get(‘/events/eventKeyA’);

will cause /events to be flushed first, even though this particular test needs /events/eventKeyA to be flushed first.

httpBackend.expectGET(‘/v1.0/events/eventKeyA’);
httpBackend.expectGET(‘/v1.0/events’);
service.get(‘/events’);
service.get(‘/events/eventKeyA’);

The alternative above seems to cause the test to throw an error,
Error: Unexpected request: GET /v1.0/events
Expected GET /v1.0/events/eventKeyA

As for the failing Travis CI build, I did push up a new commit with the corresponding build https://travis-ci.org/angular/angular.js/builds/19426708, however it seems like 9039.2 hung. Would you be able to restart it?

[atogata]

Also, included below is the actual test using this function.

    it('should use the result of the singular response, if it resolves before the parent response', function() {
        var COURSES_RESPONSE = _makeHttpCollectionSuccessResponse([COURSE_A_RESOURCE, COURSE_B_RESOURCE, COURSE_C_RESOURCE]);

        httpBackend.expectGET('/v1.0/courses').respond(angular.copy(COURSES_RESPONSE));
        httpBackend.expectGET('/v1.0/courses/course_resource_key_a').respond(angular.copy(_extendResponse(COURSE_A_RESPONSE, {
            'singularResponse': true,
        })));

        instance.get('/v1.0/courses').then(resolveCallback, rejectCallback);
        instance.get('/v1.0/courses/course_resource_key_a').then(resolveCallback2, rejectCallback2);

        httpBackend.flushByIndex(1);

        expect(resolveCallback).not.toHaveBeenCalled();

        var result2 = resolveCallback2.mostRecentCall.args[0];

        expect(result2.singularResponse).toBeTruthy();

        httpBackend.flush();
    });

[mary-poppins]

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[atogata]

@mary-poppins I've signed the CLA again under the correct e-mail.

@pkozlowski-opensource CI build passed (https://travis-ci.org/angular/angular.js/builds/21078576), are there any updates on the status of this PR? Thank you for your time!

[mary-poppins]

CLA signature verified! Thank you!

Someone from the team will now triage your PR and it will be processed based on the determined priority (doc updates and fixes with tests are prioritized over other changes).

[Narretz]

Superseded by #14967