* The "create room" button was disabled headless due to not specifying
the imported beatmap. In visual tests it seems to work due to
selecting from the local database randomly.
* The test asserts are brought in line with expectations.
These can be tested by adding a `Task.Delay(3000);` at the end of the
`MultiplayerClient.JoinRoom` task. The reason is typically that
`Client.Room` becomes not-null but the join task still hasn't completed
yet, so e.g. the ready button is still disabled.