Building Javascript Tutorials with LearnPack

If you want to create a Javascript/Node coding tutorial, you have to use the @learnpack/node plugin in order to compile and test your exercises. Go to Compiler Plugins to see how to install the plugin.

In addition, the main file should be named app.js (or you can set the name on the learn.json), and the file for the tests, should be named tests.js (you can also set the name on the learn.json).

Unit Testing

For testing, you should install Jest with the version "24.8.0". You can install it by running the following command: npm install jest@24.8.0 -g

If you are not familiar with Jest, here are the most common tests that you will use when testing a Javascript exercise tutorial:

Testing if a variable exists

1//tests.js
2
3// rewirte library is used to avoid using import/export statements on the student code
4const rewire = require('rewire');
5  
6test('The variable "name" should exist', () => {
7  const file = rewire("./app.js");
8  const name = file.__get__("name");
9  expect(name).not.toBe(undefined);
10})

Testing a variable has the expected value

1
2// tests.js
3
4const rewire = require('rewire');
5
6test('The variable "name" should have "James" as its value', () => {
7  const file = rewire("./app.js");
8  const name = file.__get__("name");
9  expect(name).toBe("James");
10})

Testing a function exists:

1// tests.js
2
3const rewire = require('rewire');
4
5test('The function "sum" should exist', () => {
6  const file = rewire("./app.js");
7  const sum = file.__get__("sum");
8  expect(sum).not.toBe(undefined);
9})

Testing a function returns the expected value:

1// tests.js
2
3const rewire = require('rewire');
4
5test('The function "sum" should return the sum of two numbers', () => {
6  const file = rewire("./app.js");
7  const sum = file.__get__("sum");
8  expect(sum(4, 8)).toBe(12);
9})

Testing the file has specific sentence with regular expressions

1// tests.js
2
3const fs = require('fs');
4const path = require('path');
5const rewire = require('rewire');
6
7test('You have to use Math.random() function', () => {
8  const file = fs.readFileSync(path.resolve(__dirname, './app.js'), 'utf8');
9  const regex = /Math\s*\.\s*random/gm
10  expect(regex.test(file.toString())).toBeTruthy();
11})

Testing a particular string has been printed in the console

1// tests.js
2
3const rewire = require('rewire');
4let buffer = "";
5global.console.log = console.log = jest.fn((text) => buffer += text + "\n");
6
7test('You have to call console.log() with "Hello World!" as value', () => {
8  const file = rewire("./app.js");
9  expect(buffer.includes("Hello World!\n")).toBe(true);
10})

Testing a function has been called with a specific parameter

1// tests.js
2
3const rewire = require('rewire');
4global.console.log = console.log = jest.fn(text => null);
5
6test('You have to call console.log() with 50 as value', () => {
7  const file = rewire("./app.js");
8  expect(console.log).toHaveBeenCalledWith(50);
9})

Testing a function has been called a specific number of times

1// tests.js
2
3const rewire = require('rewire');
4global.console.log = console.log = jest.fn(text => null);
5
6test('You have to call console.log() twice', () => {
7  const file = rewire("./app.js");
8  expect(console.log.mock.calls.length).toBe(2);
9})

Examples

The following links are javascript coding tutorials:

• ​https://github.com/4GeeksAcademy/javascript-beginner-exercises-tutorial​

• ​https://github.com/4GeeksAcademy/javascript-arrays-exercises-tutorial​

• ​https://github.com/4GeeksAcademy/javascript-functions-exercises-tutorial​

• ​https://github.com/4GeeksAcademy/master-javascript-programming-exercises​