You could use Visual Studio 2015 Community Edition (which is free) and install the Windows Phone Developer tools. Cocos2d-x generates a VS solution for Windows 10 Universal apps. With this you can test your games on the Windows Phone Emulator…
Little warning, I wasn’t able to build the Univeral App solution for Windows Desktop (see here: Anyone got proj.win10 working?) but for mobile it seems to work fine…