Hey @steve.robey
Welcome to the community! 
So the message isnât an error, itâs just informing you that, those particular requests, donât have any Tests associated with them in the Tests tab in the Request Builder. It doesnât impact the Collection run in any way.
The issue that I can see here is that the request is returning a 404 Not Found, as you are using variables {{url}}/api/v1/users/{{username}} it might be that those are not resolving during runtime.