http://magma.ua4vjlx72wv5crhkificaeysp62hizhazipfshsdvs6jxqvhtkpllcad.onion/guide/testing-methodology.html
The software “tests” whether access to these websites is being
restricted or blocked, and if so, how it is occurring. Important data such as
network errors, DNS settings, DNS entries, HTTP codes, and HTTP headers may be
collected to assist in determining the specific blocking method that is being
used.