I am testing our status display while the FR10 bench is unavailable. The substitute returns true for every call, so an error path can be broken without any test noticing. I need representative successful, failed and malformed responses at the software boundary, rather than a screen that is permanently satisfied.
Start with the few response shapes the display actually consumes, using the documented interface and saved examples from your version; I'd make one request fail after a good reading too, because an old green value can look wonderfully healthy