Configure unit tests on local machine

https://jasmine.github.io/
https://karma-runner.github.io/latest/index.html

Write unit tests

For writing unit tests we will use the Jasmine framework.

1. Initialize NodeJS project with npm init and install jasmine:

npm init
npm install --save-dev jasmine

2. Unit tests are located in *.spec.js files. Create spec file with unit tests for sum.js, in this tutorial we will test the sum function only:

js/sum.spec.js

describe('Sample project', () => {
    it('sum should return 3', () => {
        const result = sum(1, 2);
        expect(result).toBe(3);
    });

    it('sum should return 0', () => {
        const result = sum(1, -1);
        expect(result).toBe(0);
    });
});

3. Install test runner named Karma with Chrome launcher and Jasmin plugin:

npm install --save-dev karma karma-jasmine karma-chrome-launcher

4. Create karma configuration file:

karma.conf.js

module.exports = config => {
    config.set({
        basePath: './js',
        frameworks: ['jasmine'],
        files: [
            '**/*.js'
        ],
        exclude: [
            'main.js'
        ],
        preprocessors: {},
        reporters: ['progress'],
        port: 9876,
        logLevel: config.LOG_INFO,
        autoWatch: true,
        browsers: ['Chrome'],
        singleRun: false,
        concurrency: Infinity
    });
};

5. Add test command into package.json file:

"scripts": {
  "test": "karma start karma.conf.js"
}

6. Run tests:

npm run test