The Collaborative International Dictionary of English v.0.48:

Testify \Tes"ti*fy\, v. i. [imp. & p. p. Testified; p. pr. &
   vb. n. Testifying.] [OF. testifier, L. testificari; testis
   a witness + -ficare (in comp.) to make. See -fy, and cf.
   Attest, Contest, Detest, Protest, Testament.]
   1. To make a solemn declaration, verbal or written, to
      establish some fact; to give testimony for the purpose of
      communicating to others a knowledge of something not known
      to them.
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            Jesus . . . needed not that any should testify of
            man, for he knew what was in man.     --John ii. 25.
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   2. (Law) To make a solemn declaration under oath or
      affirmation, for the purpose of establishing, or making
      proof of, some fact to a court; to give testimony in a
      cause depending before a tribunal.
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            One witness shall not testify against any person to
            cause him to die.                     --Num. xxxv.
                                                  30.
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   3. To declare a charge; to protest; to give information; to
      bear witness; -- with against.
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            O Israel, . . . I will testify against thee. --Ps.
                                                  l. 7.
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            I testified against them in the day wherein they
            sold victuals.                        --Neh. xiii.
                                                  15.
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