Testing Node.js with Mocha

mocha-talk.md

TLDW: Testing NodeJS w/ Mocha

Fundamentals:

• 6:00: Assertions -comparisons which throw exception upon failure

const assert = value => if (!value) throw new Error('assertion failure!')

• 6:54: Unit Test -asserts "unit" behaves as intended, "unit" typically a function

• 9:00: Integration Test -asserts aggregate of units or modules behave as intended (e.g. side effects done correctly, state changes etc.)

Installation Locally

• 12:00: install as dev dependency npm i -D mocha
• 12:22: Obligatory Test Example

module.exports = (req, res, next) => {
  req.requestTime = Date.now(); //add request timestamp to req object
  next(); //carry on
}

• 15:13: Unit Test Example mkdir test cd test touch request-time.spec.js

Mocha Uses GLOBALS

• 16:27: Possble reason = reduces boilerplate for tests

Create a Suite

• 18:15: creating one

describe('requestTime middleware', function () {
  // Tests go here
});

Unit Test

• 18:47: Mocha uses Node.js' assert module

const assert = require('assert');
const requestTime = require('../lib/request-time'); // our middleware

• 23:54: Create a test with it(title, callback)

describe('requestTime middleware', function() {
  it('should add `requestTIme` property to req param', function() {
    // call function
    const req = {};
    requestTime(req, null, () => {});
    
    // make assertions
    assert.ok(req.requestTime > 0);
  });
});

• 26:28: Run the test $ <app>/mocha

Integration Test

• 32:29: Tools to use npm i -D supertest : Integration tests for express framework

const assert = require('assert');
const app = require('../app');
const request = require('supertest');

describe('GET /unix-timestamp', function() {
  it('should respond with JSON obj containing timestamp', function(done) {
    //test goes here
  });
});

"Nodeback" Style

• 35:00: Nodeback example

  it('should respond with JSON obj containing timestamp', function(done) {
    request(app).get('/unix-timestamp')
      .expect(200).end((err, res) => {
      if (err) return done(err);
      assert.ok(res.body.timestamp < 1e10);
      done();
  });

Promise Style (Cleaner than Nodeback)

function() {
  return request(app).get('/unix-timestamp')
    .expect(200)
    .then(res => assert.ok(res.body.timestamp < 1e10));
}