Create UnitTest in DotNet (C# or VB.Net) for upcomming plugins

We are developing in a project and need UnitTests for the plugins. Please check the attached sample solution with test.

1. Get it running
2. Add a test to verify if Windows volume is chaning correct
3. Submit your solution in clean code

We have about 10 plugins to test. Upcomming work is planned with best work.

Needed: Visual Studio (Framework 4.6.2)
Calculated time: For this first UnitTest ~1h
For upfollowing unit tests: ~30min