A simple mocha unit test example

simple_mocha_test.js

// install test tools
// npm install mocha chai --save

/* 
  add.js
*/
function add(x, y) {
  return x + y;
}

module.exports = add;

/*
  add.test.js
*/
var add = require("./add.js")
var expect = require("chai").expect;

describe('Add function', () => {
  it('1 + 2 = 3', () => {
    expect(add(1, 2)).to.be.equal(3);
  });
});

// test command
// mocha ./add.test.js