Tests passes but failures displayed as well in Mocha.js

I'm wondering why my tests are both passing but with failures.

The code that is used to tests features is:

var fireHotKey = function (key) {
    var event = document.createEvent('HTMLEvents'),
        input = document.querySelector(SELECTOR_INPUT);

    event.keyCode = key;
    event.initEvent('keyup', false, true);
    input.dispatchEvent(event);
};

it('Should create a new tag based on user input', function (done) {
    var input = document.querySelector(SELECTOR_INPUT),
        tagsContainer = document.querySelector(SELECTOR_TAGS),
        tagName = 'sunpietro';

    input.value = tagName;

    fireHotKey(KEY_COMMA);

    document.addEventListener(EVENT_TAGS_CREATED, function () {
        expect(tagsContainer).to.contain(SELECTOR_TAG);
        expect(tagsContainer.querySelectorAll(SELECTOR_TAG)).to.have.length(1);

        done();
    });
});

What is done incorrectly?