Testing the functionalities in the link function of a directive

Question

Testing the functionalities in the link function of a directive

When working with some of my directives, I often add functions to the scope in order to manage specific logic for that directive. An example of this would be:

link: function(scope, element, attrs) {
         scope.doStuff = function() {
            //perform a series of actions that need testing
         }        
      }

I've been trying to figure out how to properly test these functions. While searching online for guidance on how to test an AngularJS directive, I came across resources primarily focused on testing changes to the element itself. Compiling the directive before each test is an option, but it resets the scope every time - something I'd like to avoid as I want to test the function when properties within the scope change.

Is there a way to access the object returned from the directive definition? This would allow me to directly call the link function and test the behavior of the scope's defined functions. Are there better methods to achieve this?

I'm using Jasmine for my testing procedures, and I prefer setting up my scope within the describe functions so I can have multiple it functions for the same scope data.

javascript angularjs jasmine

Answer 1

Answer №1

Instead of directly testing the link function itself, it's better to test the resulting outcome(s) of the directive programmatically. One approach is to write out the directive as a string and use $compile to have angular process it. Then, you can verify that everything is properly connected.

Angular's source code offers helpful examples on how to do this effectively. For instance, take a look at Angular's ngRepeat directive test.

Their approach involves setting up the directive, manipulating the scope (using $rootScope in this case), ensuring it's $digested, and then examining the generated DOM to confirm proper functionality. It's also possible to check the contents of the scope to see if the directive has made any changes.

Another interesting example is the ngClick test, which demonstrates the evaluation of browser interactions and their impact on the scope.

To provide a comprehensive illustration, here's an excerpt from the ngClick tests that encapsulates the process of testing a directive effectively:

 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);
 }));

Therefore, when assessing your scope.doStuff function, focus on testing its impact on the scope and any corresponding alterations to DOM elements rather than scrutinizing its internal operations.

Answer 2

Instead of directly testing the link function itself, it's better to test the resulting outcome(s) of the directive programmatically. One approach is to write out the directive as a string and use $compile to have angular process it. Then, you can verify that everything is properly connected.

Angular's source code offers helpful examples on how to do this effectively. For instance, take a look at Angular's ngRepeat directive test.

Their approach involves setting up the directive, manipulating the scope (using $rootScope in this case), ensuring it's $digested, and then examining the generated DOM to confirm proper functionality. It's also possible to check the contents of the scope to see if the directive has made any changes.

Another interesting example is the ngClick test, which demonstrates the evaluation of browser interactions and their impact on the scope.

To provide a comprehensive illustration, here's an excerpt from the ngClick tests that encapsulates the process of testing a directive effectively:

 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);
 }));

Therefore, when assessing your scope.doStuff function, focus on testing its impact on the scope and any corresponding alterations to DOM elements rather than scrutinizing its internal operations.

Answer 3

Answer №2

If necessary, it is feasible to conduct unit testing directly on the link method of a directive. Take a look at the unit tester within the angular-ice module: "testing a directive configuration"

For instance, you can refer to: https://github.com/bverbist/angular-ice/blob/master/app/components/icebank/bank-account-number-directive_link_test.js

In your scenario, retaining a reference to the scope object passed to the directive's link method allows for direct testing of the doStuff function within that scope.

Answer 4

If necessary, it is feasible to conduct unit testing directly on the link method of a directive. Take a look at the unit tester within the angular-ice module: "testing a directive configuration"

For instance, you can refer to: https://github.com/bverbist/angular-ice/blob/master/app/components/icebank/bank-account-number-directive_link_test.js

In your scenario, retaining a reference to the scope object passed to the directive's link method allows for direct testing of the doStuff function within that scope.

Answer 5

Answer №3

I approached this problem in a slightly different way.

For those instances where your directive's link function is basic and does not require the third argument (attrs), consider replacing the link function with a controller.

app.directive('loadIndicator', function() {
  return {
    restrict: 'E',
    replace: true,
    templateUrl: 'blahblah/indicator.html',
    controller: 'LoadIndicatorController'
  };
});

Just like how scope and element are passed as arguments to a directive's link function, these two can also be injected into a controller for easier testing as $scope and $element.

If you have experience creating controllers and conducting unit tests on them, then this approach will be quite straightforward.

Answer 6

I approached this problem in a slightly different way.

For those instances where your directive's link function is basic and does not require the third argument (attrs), consider replacing the link function with a controller.

app.directive('loadIndicator', function() {
  return {
    restrict: 'E',
    replace: true,
    templateUrl: 'blahblah/indicator.html',
    controller: 'LoadIndicatorController'
  };
});

Just like how scope and element are passed as arguments to a directive's link function, these two can also be injected into a controller for easier testing as $scope and $element.

If you have experience creating controllers and conducting unit tests on them, then this approach will be quite straightforward.

Answer 7

Answer №4

In response to a comment by @sqlexception, it is important to really grasp the scope of the directive. It is not difficult to do so. The key is not to alter your code just to pass your tests; rather, your tests should align with your code.

To access the directive's scope, compile as follows:

var element = $compile(<directive's html>).($scope)

where $scope is defined as $scope = $rootScrope.$new(). You can then retrieve the isolate scope using element.scope()

I recently wrote a brief blog post on this topic, available at Testing a Linking Function, which includes a helpful Plunker demonstration.

Answer 8

In response to a comment by @sqlexception, it is important to really grasp the scope of the directive. It is not difficult to do so. The key is not to alter your code just to pass your tests; rather, your tests should align with your code.

To access the directive's scope, compile as follows:

var element = $compile(<directive's html>).($scope)

where $scope is defined as $scope = $rootScrope.$new(). You can then retrieve the isolate scope using element.scope()

I recently wrote a brief blog post on this topic, available at Testing a Linking Function, which includes a helpful Plunker demonstration.

Answer 9

Answer №5

 describe('click event triggering function', inject(function($rootScope, $compile) {
   var localScope = $rootScope.$new();
   element = $compile('<div ng-click="doIt()"></div>')(localScope);
   localScope.$digest();
   expect(localScope.$$childHead.doIt()).toBeDefined();
 }));

Using $$childHead as a reference helped me solve a similar issue I was facing in my testing scenario by allowing me to test functions that were not being triggered.

Answer 10

 describe('click event triggering function', inject(function($rootScope, $compile) {
   var localScope = $rootScope.$new();
   element = $compile('<div ng-click="doIt()"></div>')(localScope);
   localScope.$digest();
   expect(localScope.$$childHead.doIt()).toBeDefined();
 }));

Using $$childHead as a reference helped me solve a similar issue I was facing in my testing scenario by allowing me to test functions that were not being triggered.

Testing the functionalities in the link function of a directive

Answer №1

Answer №2

Answer №3

Answer №4

Answer №5

Similar questions

Using Google Maps to Cluster Markers on Your Website

Retrieving table information using javascript

Does Angular2 restrict directives to just one root element?

Caution: PropType validation failed - The prop `rrrr` provided to `sportsMockUpStandard` is not valid

Various results can be produced based on the .load() and .resize() or .scroll() functions despite using the same calculation methods

What is the most efficient way to check for the presence and truthiness of a nested boolean in Node.js?

The Angular masonry directive is causing inner elements to disappear with an error message popping up: "Oh no! Masonry is

What steps should be taken to make an object rotate in the opposite direction of the cursor

Ways to access the variables of an object that initiated a function, leading to another function being called

Issues with displaying calendar items on the React timeline are only resolved after pressing F12 or resizing the

Verify whether the items within the ng-repeat directive already contain the specified value

AngularJS Tip: Ensuring addClass is not called on directive during page load

Using AngularJS and Express to send intricate form data to a RESTful API

The AngularJS filter with momentjs for dates is producing excessive output

A helpful tip for creating line breaks within a Vue JS v-for loop using CSS

Proper method for verifying line-clamp in a Vue component

Creating dynamic links within HTML through real-time updating

Load full html content, including doctype, into a jQuery container | Block scripts from running in iFrames

Tips for dividing the rows within an array using the match() function?

When trying to integrate Angular.ts with Electron, an error message occurs: "SyntaxError: Cannot use import statement