Unit testing AngularJS Directives with Jest

All we need is an easy explanation of the problem, so here it is.

I feel I am missing something crucial in this extremely simplified angular directive unit test:

import * as angular from 'angular'
import 'angular-mocks'

const app = angular.module('my-app', [])

app.directive('myDirective', () => ({
    template: 'this does not work either',
    link: (scope, element) => { // have also tried compile fn
        console.log('This does not log')
        element.html('Hi!')
    }
}))

describe('myDirective', () => {
    var element, scope

    beforeEach(app)

    beforeEach(inject(($rootScope, $compile) => {
        scope = $rootScope.$new()
        element = $compile('<my-directive />')(scope)
        scope.$digest()
    }))

    it('should actually do something', () => {
        expect(element.html()).toEqual('Hi!')
    })
})

When jest runs it appears the directive has not been linked/compiled/whatever

 FAIL  test/HtmlToPlaintextDirective.spec.js
  ● myDirective › should actually do something

    expect(received).toEqual(expected)

    Expected value to equal:
      "Hi!"
    Received:
      ""

How to solve :

I know you bored from this bug, So we are here to help you! Take a deep breath and look at the explanation of your problem. We have many solutions to this problem, But we recommend you to use the first method because it is tested & true method that will 100% work for you.

Method 1

Updated answer:

You’re right things don’t work as expected when importing everything in a single file.

Digging into things it looks like you’re running into some magic that Babel/Jest does to support browser scripts that rely on globals (like AngularJS).

What’s happening is that your module’s angular variable is not the same as the global angular variable that is visible to angular-mocks.

You can check this by running this at the top of one of your tests:

import * as angular from 'angular'
import 'angular-mocks'

console.log(angular === window.angular); // `false` in Jest!

console.log(angular.mock); // undefined
console.log(window.angular.mock); // `{...}` defined

To work around this you just need to use the global angular variable in your tests.

src/__test__/all-in-one.test.js:

import "angular";
import "angular-mocks";

/*
Work around Jest's window/global mock magic.

Use the global version of `angular` that has been augmented by angular-mocks.
*/
var angular = window.angular;


export var app = angular.module('app', []);

app.directive('myDirective', () => ({
    link: (scope, element) => {
        console.log('This does log');
        scope.content = 'Hi!';
    },
    template: 'content: {{content}}'
}));


describe('myDirective', function(){
    var element;
    var scope;

    beforeEach(function(){
        angular.mock.module(app.name);
    });

    it('should do something', function(){
        inject(function(
            $rootScope,
            $compile
        ){
            scope = $rootScope.$new();
            element = $compile('<my-directive></my-directive>')(scope);
            scope.$digest();
        });

        expect(element.html()).toEqual('content: Hi!');
    });
});

Original answer: (This worked because I was accidentally using the global version of angular inside my test.)

The Angular module under test isn’t being initialised correctly in your tests.

Your call to beforeEach(app) isn’t correct.

Instead you need to use angular.mock.module("moduleName") to initialise your module.

describe('myDirective', () => {
    var element, scope

    // You need to pass the module name to `angular.mock.module()`
    beforeEach(function(){
        angular.mock.module(app.name);
    });


    // Then you can set up and run your tests as normal:
    beforeEach(inject(($rootScope, $compile) => {
        scope = $rootScope.$new()
        element = $compile('<my-directive></my-directive>')(scope)
        scope.$digest()
    }))

    it('should actually do something', () => {
        expect(element.html()).toEqual('Hi!')
    })
});

And then your test works as expected for me:

 PASS  src\__test__\app.test.js
  myDirective
    √ should do something (46ms)

For reference, here is the full app and test:

src/app/app.module.js:

import * as angular from 'angular'

export var app = angular.module('app', []);

app.directive('myDirective', () => ({
    link: (scope, element) => {
        console.log('This does log');
        scope.content = 'Hi!';
    },
    template: 'content: {{content}}'
}))

src/__test__/app.test.js:

import {app} from "../app/app.module";
import "angular-mocks";

describe('myDirective', function(){
    var element;
    var scope;

    beforeEach(function(){
        angular.mock.module(app.name);
    });

    beforeEach(inject(function(
        $rootScope,
        $compile
    ){
        scope = $rootScope.$new();
        element = $compile('<my-directive></my-directive>')(scope);
        scope.$digest();
    }));

    it('should do something', function(){
        expect(element.html()).toEqual('content: Hi!');
    });
});

Method 2

I ran into the same baffling behavior a couple years later and I wanted to share what I found

If you transpile the test using babel and look at the imports you will find something similar to the following

var _interopRequireWildcard = require("@babel/runtime/helpers/interopRequireWildcard");
var angular = _interopRequireWildcard(require("angular"));
require("angular-mocks");

_interopRequireWildcard currently has the following implementation

function _interopRequireWildcard(obj) {
  if (obj && obj.__esModule) {
    return obj;
  } else {
    var newObj = {};

    if (obj != null) {
      for (var key in obj) {
        if (Object.prototype.hasOwnProperty.call(obj, key)) {
          var desc = Object.defineProperty && Object.getOwnPropertyDescriptor ? Object.getOwnPropertyDescriptor(obj, key) : {};

          if (desc.get || desc.set) {
            Object.defineProperty(newObj, key, desc);
          } else {
            newObj[key] = obj[key];
          }
        }
      }
    }

    newObj.default = obj;
    return newObj;
  }
}

In short it creates a new object and copies all the properties from the imported object. This is why angular === window.angular is false. It also explains why angular.mock isn’t defined, it didn’t exist when _interopRequireWildcard made a copy of the module

Given that there are a couple additional ways to solve the problem in addition to the accepted answer

Instead of using import * as angular from 'angular' using import angular from 'angular' should avoid the behavior because _interopRequireDefault does not return a different object. (However, if you are using TypeScript it may not resolve the types for ‘angular’ correctly with this method)

Another option would be to import angular twice:

import 'angular'
import 'angular-mocks'
import * as angular from 'angular'

Note: Use and implement method 1 because this method fully tested our system.
Thank you 🙂

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0

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