tobi only returns the body contents for a "successful" response (where the status is between 200 and 300) which precludes testing the representation returned in a 404 page, 400/422 errors returned for invalid forms input and a 500 error (admittedly hard to recreate normal processing).
shit yeah that's not good one sec
there's a pull request to fix this: #57
Fixed body on non-2xx response. Closes #56