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How to test behavior in the link function of a directive

rated 0 times [ 193] [ 1] / answers: 1 / hits: 33770 / 12 Years ago, thu, november 15, 2012, 12:00:00

In some of my directives, I'm adding functions to the scope to handle logic specific for the directive. For example:

link: function(scope, element, attrs) {

         scope.doStuff = function() {

            //do a bunch of stuff I want to test

         }        

      }

How do I go about testing that function? I googled around for how test a directive, but the things I found were more about testing changes on the element. I can certainly compile my directive before each of my tests, but that would wipe out my scope every time. I want to test the function as properties in my scope changes.

Is there any way to get a hold of the object that is returned from the directive definition? Then I could just call the link function directly and test the behavior of each of the functions defined on the scope. Is there a better way to do all this?

I'm using Jasmine to run my tests, and I'm wanting to my scope setup in the describe functions, so I can have multiple it functions for the same scope data.

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3 Years ago

answered 12 Years ago parker · Accepted Answer

Basically, rather than test the link function itself, you'd test the outcome(s) of the directive programmatically. What you would do is write out the directive to a string, and use $compile to have angular process it. Then you test the output to make sure everything is wired up correctly.

Angular's source is full of good examples of how to do this... for example Angular's test of the ngRepeat directive

You can see what they're doing is setting up the directive, Changing the scope (in this case $rootScope) making sure it's $digested, and then testing the DOM it outputs to make sure everything is wired up correctly. You can also test what's in the scope, if the directive is altering that.

The test for ngClick is also pretty interesting, because it shows testing of a browser interaction and it's effect on the scope.

For sake of completeness, here's a snippet from the ngClick tests that I think sums up testing a directive fairly well:

 it('should get called on a click', inject(function($rootScope, $compile) {

   element = $compile('<div ng-click=clicked = true></div>')($rootScope);

   $rootScope.$digest();

   expect($rootScope.clicked).toBeFalsy();



   browserTrigger(element, 'click');

   expect($rootScope.clicked).toEqual(true);

 }));

So in the case of your scope.doStuff function, I wouldn't test what it's doing, so much as I'd test whatever it's affected on the scope, and it's subsequently effected DOM elements.