// Polyfill for creating CustomEvents on IE9/10/11
// code pulled from:
// https://github.com/d4tocchini/customevent-polyfill
// https://developer.mozilla.org/en-US/docs/Web/API/CustomEvent#Polyfill
if (!window.CustomEvent || typeof window.CustomEvent !== 'function') {
    var CustomEvent = function(event, params) {
        var evt;
        params = params || {
            bubbles: false,
            cancelable: false,
            detail: undefined
        };

        evt = document.createEvent("CustomEvent");
        evt.initCustomEvent(event, params.bubbles, params.cancelable, params.detail);
        return evt;
    };

    CustomEvent.prototype = window.Event.prototype;
    window.CustomEvent = CustomEvent; // expose definition to window
}

Add CustomEvent polyfill for tests
Add CustomEvent polyfill for tests
