I overlooked the fact that setting the AuthenticationScheme values does not actually achieve what we want. By default, schemes are set to .AspNetCore.{AuthenticationScheme} and this leads to names like .AspNetCore..AspNetCore.Identity.Application since cookies middleware adds the .AspNetCore. prefix by default. We can remove the .AspNetCore. from the prefix of the authentication scheme.

Still investigating the why there are also cookies like .AspNetCore.Microsoft.AspNetCore.Identity.ExternalLogin.

Edit: Ignore the ExternalLogin cookie issue. That is a really old legacy name for the cookie and the test is only checking it for non-existence.

fyi @natemcmaster