Angular Code Coverage wrong output

Question

My stack is: Angular.js, Karma, Karma-coverage (Istanbul) and Jasmine.

I have been running Code Coverage analysis over my app, the problem, and thus the question, is that I get Service A marked as covered by tests (in green) when it actually does not have any tests associated.

I suspect that the following scenario is to blame:

I know that Service A is used by Controller B.
Controller B is covered by tests, and the Code Coverage results mark it correctly as covered by tests.
Service A is not being mocked when testing Controller B.

I think that since service A is indirectly called by Controller B's tests, I get the wrong result.

Any ideas? Am I suspecting the right thing? Is there any ways around it so I can get an accurate test coverage result in this aspect?

Thanks in advance!

Brian Lewis · Accepted Answer · 2014-11-19 03:28:25Z

3

Unfortunately, this is how code coverage is evaluated. If the code is executed, it is considered to be "covered". Luckily, there is something you can do to reduce some of the false positives. You can mock out your dependencies!

The following example will execute a jasmine spy instead of the actual service:

describe('Controller Tests', function() {
  var $scope, mockServiceA;

  beforeEach(module('app', function($provide) {
    mockServiceA = jasmine.createSpyObj('mockServiceA', ['foo']);
    $provide.value('ServiceA', mockServiceA);
  }));

  beforeEach(inject(function($rootScope, $controller) {
    $scope = $rootScope.$new();
    $controller('ControllerB', {
      $scope: $scope
    });
  }));

  describe('ControllerB', function() {
    it('should call mock service', function() {
      expect(mockServiceA.foo).not.toHaveBeenCalled();
      $scope.useServiceA();
      expect(mockServiceA.foo).toHaveBeenCalled();
    });
  });
});

Here is a working Plunker: http://plnkr.co/edit/x8gQQNsHT0R5n5iJSxKw?p=info

answered Nov 19, 2014 at 3:28

Brian Lewis

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3 Comments

franleplant Over a year ago

Thank you for you answer! Mocking rocks! But sometimes mocking complex components that have a lot of dependencies is too obtrusive. It is good to have this in mind when evaluating and analyzing Code coverage reports.

Brian Lewis Over a year ago

An alternative approach to mocking the service, as described above, would be to spyOn().and.callFake(). I have found that unit tests end up being a little more work than the code they are testing but that is the price we pay for stability.

franleplant Over a year ago

Thanks! For those who are interested, this is the link to Jasmine's doc about spies jasmine.github.io/2.0/introduction.html#section-Spies

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