Battery.spec.3.2 fails on windows phone 8.1

This failure is happening because the tests assume that battery status wouldn't change between mocks, when event listener is added, but it actually changes back to 100% on windows phone 8.1:

navigator.battery._status({
    level : 5,
    isPlugged : false
});

window.addEventListener("batterylow", onEvent, false);

navigator.battery._status({
    level: 20,
    isPlugged: false
});

Event listener should be added before first mock so that windows wouldn't have the time to change the battery status in between mocks.