Writing tests for services using Karma

Testing AngularJS services is crucial to ensure your application’s business logic functions correctly. Karma (test runner) and Jasmine (testing framework) provide a powerful combination for unit testing services in AngularJS.

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1. Setting Up Karma and Jasmine for Testing

A. Install Required Dependencies

Use npm to install necessary testing libraries:

npm install --save-dev karma karma-jasmine jasmine-core karma-chrome-launcher angular-mocks

B. Configure Karma

Create a karma.conf.js file:

module.exports = function(config) {
    config.set({
        frameworks: ['jasmine'],
        browsers: ['Chrome'],
        files: [
            'node_modules/angular/angular.js',
            'node_modules/angular-mocks/angular-mocks.js',
            'app.js',  // Your AngularJS app file
            'services/*.js',  // Your service files
            'tests/*.spec.js'  // Your test files
        ],
        reporters: ['progress'],
        singleRun: true
    });
};

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2. Writing a Sample AngularJS Service

A. Sample MathService

app.service('MathService', function() {
    this.add = function(a, b) {
        return a + b;
    };

    this.subtract = function(a, b) {
        return a - b;
    };
});

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3. Writing Unit Tests for the Service

A. Basic Test for MathService

Create mathService.spec.js inside the tests/ directory:

describe('MathService', function() {
    var MathService;

    beforeEach(module('myApp')); // Load Angular module
    beforeEach(inject(function(_MathService_) {
        MathService = _MathService_;
    }));

    it('should add two numbers correctly', function() {
        expect(MathService.add(2, 3)).toBe(5);
    });

    it('should subtract two numbers correctly', function() {
        expect(MathService.subtract(5, 3)).toBe(2);
    });
});

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4. Testing a Service with API Calls ($httpBackend)

A. Sample UserService Making HTTP Request

app.service('UserService', function($http) {
    this.getUser = function(userId) {
        return $http.get('/api/users/' + userId);
    };
});

B. Unit Test Using $httpBackend

describe('UserService', function() {
    var UserService, $httpBackend;

    beforeEach(module('myApp'));
    beforeEach(inject(function(_UserService_, _$httpBackend_) {
        UserService = _UserService_;
        $httpBackend = _$httpBackend_;
    }));

    it('should fetch user data', function() {
        var mockUser = { id: 1, name: 'John Doe' };
        $httpBackend.expectGET('/api/users/1').respond(200, mockUser);

        var result;
        UserService.getUser(1).then(function(response) {
            result = response.data;
        });

        $httpBackend.flush(); // Simulate server response

        expect(result).toEqual(mockUser);
    });

    afterEach(function() {
        $httpBackend.verifyNoOutstandingExpectation();
        $httpBackend.verifyNoOutstandingRequest();
    });
});

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5. Running the Tests with Karma

Execute the tests using the following command:

npx karma start karma.conf.js