Migrate Test projects here

[jasonswearingen]

tests currently written in xunit.

xunit WAS integrated into NotNot.Core prior to the NotNot-MonoRepo migration, but removed because it broke nuget publishing.

this issue is to migrate the code here, however not nessicarily get it working. Idea is to try out TUnit first (see M001 issue)

[jasonswearingen]

continuing use of xunit v2. still need to port BCL test code though