Fix tests locally and in CI
Fix tests locally and in CI

When tests run locally from within VS, we use net472 so that TestDriven can run them quickly. In CI, we use net5, which requires Microsoft.TestPlatform.ObjectModel (see https://github.com/microsoft/vstest/issues/2469#issuecomment-666998302)

toddams/RazorLight,toddams/RazorLight