Consider changing to NUnit to easily allow capturing console output

Capturing console output in xUnit 2 is annoying, as you have to work with test classes and constructor injection. Writing the code to support this is annoying, complex and brittle. An option might be to use NUnit as the test framework.
See https://stackoverflow.com/questions/46405753/how-do-i-get-nunit3-console-to-output-my-debug-to-screen-on-a-windows-box

Side note: due to us using FsUnit, the actual test code might not even change much.