FindMetric iterates through mfs to find the first metric family matching name.

FromHTTPResponse parses the prometheus metrics from the given *http.Response.

MustFindMetric returns the matching metric, or if no matching metric could be found, it calls tb.Log with helpful output of what was actually available, before calling tb.FailNow.

MustGather calls g.Gather and calls tb.Fatal if there was an error.