Many of my tests make use of the NullLogger defined in:

https://github.com/aspnet/Logging/tree/dev/src/Microsoft.Extensions.Logging.Testing

As far as I can tell, this package isn't published to nuget.org, so I find myself cutting and pasting it and then possibly updating it with every AspNetCore release.