OK, I think I see what is happening here. We're referencing xunit 1.9.2 and AutoFixture.Xunit is referencing 1.8. NuGet has put binding redirects into app.config which means stuff gets resolved at runtime and everything works. I guess the .NET compiler also respects the binding redirects and realises that it doesn't have to issue the warning but the Mono compiler does not.

Since these are test projects I think it's fine to use the `<NoWarn>` element but if we ever find ourselves having to do this for the non-test projects I believe we should use `<WarningsNotAsErrors>1701</WarningsNotAsErrors>` so that we still get the warning in VS when binding redirects are missing.