Microsoft Universal Apps and Unit Testing, trouble with AppModel version

Question

I started a new Solution to try the Universal Apps. To test my code I want to add a unit test project (windows phone 8.1), but if I do so I get this error message when I start a unit test:

Error : DEP0700 : Registration of the app failed. Windows cannot install package 808f4bed-6f93-48b9-9b63-071d68456607 because this package requires a higher Windows version. The package requested Windows version 6.3 with AppModel version 1, while the current Windows version is 6.3 with AppModel version 0. (0x80073cfd)

What does this AppModel version 1 and AppModel version 0 mean, and how can I fix this?

Or is there and another way to do unit tests in the context of Microsoft Universal Apps?

This is what my project structure looks like

Update

Windows Phone 8.1 Project + Windows Phone 8.1 Unit Test = don't work Windows Phone 8 Project + Windows Phone 8 Unit Test = works

But I still don't have a clue how I can get the Windows Phone 8.1 to work.

btw my windows version (Windows 8.1 Update)

PS C:\Windows\system32> [System.Environment]::OSVersion.Version

Major  Minor  Build  Revision
-----  -----  -----  --------
6      3      9600   0

Answer 1

On Universal Windows App msdn site I see following note:

Note These samples require Windows 8.1 and Microsoft Visual Studio 2013 with Microsoft Visual Studio 2013 Update 2 or later. They don't compile in Microsoft Visual Studio 2012 for Windows 8

I checked my own current Visual Studio Installation 'About' page and see that I have VST 2013 Update 1. Maybe you have to explicitly update your Visual Studio version, it doesn't seem to happen by default.

I also checked the Microsoft Visual Studio 2013 Update 2 download page and that explicitly states

It includes tools for Windows Phone 8.1 development.