Hi @hobovsky
For the sonar-dotnet plugins (C# and VB .NET), we don’t push unit test results data to SonarQube. Historically, it has been a missing feature of the plugin and we’ve had issue #886 to track it.
However, recently we decided to close the issue as Won't fix - you can read the motivation in this comment.
Having said that, you can import test data using Generic Test Data and it will work (see DotNet core code coverage - #7 by Thibault_DESAULES).