Collins Russian Dictionary 2nd Edition © HarperCollins Publishers 2000, 1997:
attest [əˈtɛst] vi
to attest to(demonstrate) свиде́тельствовать (impf) о +prp ; (LAW) свиде́тельствовать (засвиде́тельствовать perf)
* is used to mark translations which have irregular inflections. The Russian-English side of the dictionary gives inflectional information.