AngularJS Unit Test element.bind

Question

Inside a directive of mine called by data-type-ahead I have the following, in a series of events:

$scope.test = 5;

// Bind blur event and clear the value of 
element.bind('blur', function(){
    $scope.test = 0;
});

I have tried a multitude of things to use in a unit test to correctly test the functionality of this blur event however I have not been successful. I have seen mention of the function triggerHandler. Here is my attempt at the unit test:

//Inject $compile and $rootScope before each test.
beforeEach(inject(function(_$compile_, _$rootScope_) {
    $compile = _$compile_;
    $rootScope = _$rootScope_;

    $scope = $rootScope.$new();
    $scope.test = 5

    html = angular.element('<input type="text" data-type-ahead/>');

    //Apply $scope to directive html.
    directive = $compile(html)($scope);

    //Trigger digest cycle.
    $scope.$digest();
}));

it('should trigger the events bound to the blur event on the directive', function() {
    html.triggerHandler('blur')
    expect($scope.test).toEqual(0);
});

However this is failing because $scope.test is remaining on 5. Is it the html element is incorrect, do I need another $digest or $apply for after I trigger the event?

yccteam · Accepted Answer · 2017-11-14 08:25:22Z

You have 2 ways of getting this to work. The first is adding a timeout to your method (docs):

// somewhere above add - 
var originalTimeout = jasmine.DEFAULT_TIMEOUT_INTERVAL;
jasmine.DEFAULT_TIMEOUT_INTERVAL = 10000;

// in your beforeEach

beforeEach(function(){
 html.triggerHandler('blur');
  setTimeout(function(){
  done();
 }, 1000);
});

it('should trigger the events bound to the blur event on the directive',  
   function() {
    expect($scope.test).toEqual(0);
   }
);

I believe this to be "less good" practice (bad or worse is too negative a word for testing - the moment you test, you are already better :)). In general, I try to avoid testing async, because eventually my methods (a.k.a. units) are sync inside.

The "better practice" would be to write the method that changes the value like this:

// in the directive's ctrl
this.changeValue = function changeValue{
  $scope.test = 0;
}

// later on set the watcher
// Bind blur event and clear the value of 
$element.bind('blur', this.changeValue);

And then test the method itself instead of testing it async. You could test the $element.bind (via the spyOn(element, 'bind')) if you like to see that your ctrl/link methods create the binding.

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