Yes, that was it. Coupled with my lack of understand of how to return a non-200 result code back to client. I think i have this figured out now.
conn
|> put_status(:not_found)
|> json(%{"Errors" => "Not found"})
Will allow the client/test to receive a normal HTTP response. If an error is raised, like a match error, that will automatically return a 500 result code and the test has to use the assert_error_sent
