Tests for UWP configuration

[wilhelmberg]

I spent the better part to the day trying to make existing tests work with an UWP configuration.
Problem being that UWP apps are a completely different kind of breed, eg no console apps and unit test support is not yet the same like for other framework versions.

• nunit engine is not yet compatible with UWP apps.
  • I did try the NUnit Visual Studio Templates (Github / VS Extension Gallery) that have UWP support.
    Tests did run correctly (as a separate app), but VS didn't recognize any of the nunit specific code highlighting everything as errors.
• xunit: seems to be the only UWP compatible one at the moment, but syntax is different to nunit which would mean rewriting all tests
• VS does provide a Unit Test App (Universal Windows) template of its own, but the available methods seem subpar to nunit, e.g. DataSource attribute to feed different data do a test method seems to accept database connections only. Haven't found a way to feed a list of file names like with nunit's TestCaseSource.
  Also different syntax compared to nunit.