00_Testing_with_mockery

// This is a basic demonstration of using mockery alongside mocha/chai
// for unit testing in node.

01_bar-module.js

// This is the module we will test.

import bob from './bob';

function bar() {
  return bob()
}

export default bar;

02_bob-dependency.js

// This is a dependency consumed by our module that we will mock.

function bob() {
  return 'real bob';
}

export default bob;

03_bar.test.js

// The test for our module

import { expect } from 'chai';
import { configureMockery } from '_common/tests';

describe('When executing with a mocked bob', () => {
  const bobStub = () => `mocked bob result`;
  
  configureMockery((m) => {
    m.registerMock('./bob-dependency', bobStub);
  });

  it('Then the mock result should be returned', () => {
    const { default: subject } = require('./bar-module');

    const expected = 'mocked bob result';
    const actual = subject();

    expect(actual).to.equal(expected);
  });
});

04_configureMockery.js

// This is our test helper

import mockery from 'mockery';

export const configureMockery = (conf) => {
  before(() => {
    mockery.enable({
      useCleanCache: true,
      warnOnReplace: false,
      warnOnUnregistered: false
    });
    conf(mockery);
  });

  after(() => {
    mockery.deregisterAll();
    mockery.disable();
  });
};