How to test document.addEventListener('keydown', cb) with Mocha & Sinon?

Question

I'm trying to figure out the best way for testing this method:

document.addEventListener("keydown", function (event) {
    var modifiers = event.altKey || event.ctrlKey || event.metaKey ||
                    event.shiftKey;
    var mapped    = map[event.which];

    if (!modifiers) {
      if (mapped !== undefined) {
        event.preventDefault();
        self.emit("move", mapped);
      }
    }
  });

I'd like to ensure that if the keys are modifiers or if the keys are not mapped, nothing happens, however, if they are, to spy on the self.emit function.

Answer 1

I could do it with sinon. Here is my solution:

it('adds listener events', function() {
  sinon.spy(document, 'addEventListener')
  sinon.spy(window, 'addEventListener')

  expect(document.addEventListener.calledOnce).not.to.be.true
  expect(window.addEventListener.calledOnce).not.to.be.true

  subject.myFunc()

  expect(document.addEventListener.calledOnce).to.be.true
  expect(window.addEventListener.calledOnce).to.be.true
})

In my case I had to test window focus and document click for example.

Hope it helps