Microsoft is making it much easier for developers to test their game for Windows 10 Mobile by releasing a brand new Windows Application Development tool. This new command line utility allows developers to deploy and sideload apps onto their Windows 10 Mobile device connected to their computer via USB cable, without requiring the full Visual Studio.
To download the application development tool, developers need to download the Windows 10 SDK from the Windows 10 Developer Tools page on a computer with the Windows Insider Preview build 10166 or newer. There is no need to download and install Visual Studio 2015 for this form of testing.
Before trying to deploy and app onto a Windows 10 Mobile device, developers need to go into your Settings > Update & Security > Development and turn on Developer Mode, after which the phone will need to be restarted. Also, the phone needs to be running the latest Windows 10 Mobile Insider Preview build 10149.
To learn more and see this in action, you can watch this video here.
Further reading: Developers, Microsoft, Windows 10 Mobile
