After do some tests, I finally find out this is an issue in Windows 10 UAP with VS 2015 CTP6.
The main reason of the issue is we used two different test namespace, Microsoft.VisualStudio.TestTools.UnitTesting & Microsoft.VisualStudio.TestPlatform.UnitTestFramework
Now we need to deeply view on it.
This is the namespace tool when you use testm/testc, the VS IDE will help you to add it to the namespace.
This is the default namespace when you created a new Win10 UAP test project.
By viewing the name of the namespace, test platform may a specified for testing UAP, that’s it.