I like to respond with 418 as the catch all response code for mock web services for requests that dont match any installed expected requests. The reasoning is

I like to respond with 418 as the catch all response code for mock web services for requests that dont match any installed expected requests. The reasoning is sometimes 404 is a valid mock response for some test cases, so I needed the "404 for mocks" that would never appear on any legit service. Very clearly highlights when something is going wrong on a test.