How to mock dependencies for unit tests with ES6 Modules

Question

I\'m trying to fiddle with Ecmascript 6 modules using webpack + traceur to transpile to ES5 CommonJS, but I\'m having trouble successfully unit testing them.

I tried

Answer 1

If you are using Webpack another option that has a little more flexibility than rewire is inject-loader.

For example, in a test that is bundled with Webpack:

describe('when an alert is dismissed', () => {

  // Override Alert as we need to mock dependencies for these tests
  let Alert, mockPubSub

  beforeEach(() => {
    mockPubSub = {}
    Alert =  require('inject!./alert')({
      'pubsub-js': mockPubSub
    }).Alert
  })

  it('should publish \'app.clearalerts\'', () => {
    mockPubSub.publish = jasmine.createSpy()
    [...]
    expect(mockPubSub.publish).toHaveBeenCalled()
  })
})

inject-loader, in a similar manner to proxyquire at least allows one to inject dependencies before importing whereas in rewire you must import first and then rewire which makes mocking some components (e.g. those that have some initialization) impossible.