Mocha Sinon Fake Timer

mocha-timer.js

const sinon = require('sinon');

module.exports = function() {
  /**
   * Fake timers (setImmediate, setTimeout)
   */
  before(function() {
    this.clock = sinon.useFakeTimers(new Date());
  });

  after(function() {
    this.clock.restore();
  });
};

mocha-timer.spec.js

const assert = require('assert');

const app = require('express')();

describe('mocha-timer', function() {
  // usage of the timer in a test
  require('./mocha-timer')();

  it('loads', function() {
  });

  it('injects sinon', function() {
    assert(this.clock);
  });

  it('mocks setImmediate', function() {
    let called = false;
    setImmediate(() => {
      called = true;
    });

    assert(Object.keys(this.clock.timers).length == 1);

    this.clock.runAll();

    assert(called);
  });

  it('mocks nested setImmediate', function() {
    let called = false;

    setImmediate(() => {
      setImmediate(() => {
        called = true;
      });
    });

    assert(Object.keys(this.clock.timers).length == 1);
    
    this.clock.runAll();

    assert(called);
  });

  it('mocks async setImmediate', function() {
    let called = false;

    setImmediate(async () => {
      // WIP
      const promise = new Promise((done) => {
        require('http').get('http://nodejs.org/dist/index.json', (res) => {
          called = true;
          done();
        });
      });

      return await promise;
    });

    this.clock.runAll();

    // it does not wait for the promise resolution
    // assert(called);
  });
});