MakeAPIServer is used during testing to create an HTTP server to return fixtures if the request matches.

MakeHookRequest creates and returns a new http.Request that resembles a GitHub hook request, including the correct event type and reading and sending a fixture as a JSON body.

ReadJSONFixture reads a filename into a map, and fails the test if it is unable to open or parse the file.

UnmarshalJSON unmarshals a byte-slice to a map.