Hi @hobovsky and welcome to the community !
Thank you for your insights, that will certainly help us when doing some improvements on the UX of that Scanner.
Just to be super clear but you might have discover that on your own : sonar.sources and sonar.test, in the context of the Scanner for MSBuild, are meant to be filled by it, with automatic detection, so you don’t have to provide values at all for that.
That being said, and as per the wiki page you discover (this one is pretty new BTW, it will be included in the docs very soon), make sure that, by providing corresponding tags and, if needed, projects Guid (are you targeting a .NET core project BTW ? Please note that those one are not yet fully supported, so you have, in some case, to manually put ProjectGuids either in the SLN file if you have one, or in the csproj directly) to make sure that the detection will work properly.
For tests coverage files, you will have to provide manually the nunit property, as the default behavior is to detect and fill only vstest coverage and binary files.
HTH,
Mickaël