Introduction to Karma-Jasmine

Karma-Jasmine is a popular testing framework that enables developers to write and run unit tests for JavaScript applications efficiently. It combines the powerful features of the Karma test runner with the versatile Jasmine testing library to offer a robust testing environment.

Setting Up Karma-Jasmine

To get started with Karma-Jasmine, you need to install the necessary packages using npm:

  npm install --save-dev karma karma-jasmine jasmine-core

Configuring Karma

Next, you need to configure Karma by creating a karma.conf.js file:

  module.exports = function(config) {
    config.set({
      frameworks: ['jasmine'],
      files: [
        'src/**/*.js',
        'test/**/*.spec.js'
      ],
      browsers: ['Chrome'],
      singleRun: true,
      reporters: ['progress']
    });
  };

Writing Your First Test

Creating a test file (e.g., example.spec.js):

  describe('Math functions', function() {
    it('should add two numbers correctly', function() {
      expect(1 + 1).toBe(2);
    });

    it('should subtract two numbers correctly', function() {
      expect(2 - 1).toBe(1);
    });
  });

Running Tests

To run your tests, use the following command:

  ./node_modules/.bin/karma start

Advanced API Features

Karma-Jasmine provides a variety of methods to make testing more effective:

• beforeEach and afterEach hooks to set up and tear down test environments:

      beforeEach(function() {
        // setup code
      });

      afterEach(function() {
        // teardown code
      });
    

• spyOn to mock functions:

      const foo = {
        bar: function() { return 'baz'; }
      };

      spyOn(foo, 'bar');
      foo.bar();
      expect(foo.bar).toHaveBeenCalled();
    

Complete Application Example

Let’s consider a small application to manage a list, and we’ll write tests for it.

  // app.js
  class ListManager {
    constructor() {
      this.items = [];
    }

    addItem(item) {
      this.items.push(item);
    }

    getItems() {
      return this.items;
    }
  }

  module.exports = ListManager;

  // test.spec.js
  const ListManager = require('./app');
  describe('ListManager', function() {
    let listManager;

    beforeEach(function() {
      listManager = new ListManager();
    });

    it('should add item to the list', function() {
      listManager.addItem('item1');
      expect(listManager.getItems()).toContain('item1');
    });

    it('should return the list of items', function() {
      listManager.addItem('item2');
      expect(listManager.getItems()).toEqual(['item2']);
    });
  });

By integrating the above Karma-Jasmine APIs into your workflow, you can ensure that your JavaScript applications are thoroughly tested and reliable.

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