The Collaborative International Dictionary of English v.0.48:

Test \Test\, Testa \Tes"ta\, n.; pl. E. Tests, L. Testae.
   [L. testa a piece of burned clay, a broken piece of
   earthenware, a shell. See Test a cupel.]
   1. (Zool.) The external hard or firm covering of many
      invertebrate animals.
      [1913 Webster]

   Note: The test of crustaceans and insects is composed largely
         of chitin; in mollusks it is composed chiefly of
         calcium carbonate, and is called the shell.
         [1913 Webster]

   2. (Bot.) The outer integument of a seed; the episperm, or
      spermoderm.
      [1913 Webster]

WordNet (r) 3.0 (2006):

testa
    n 1: protective outer layer of seeds of flowering plants [syn:
         testa, episperm, seed coat]