We propose a concurrent program testing technique that is a specification-based one and uses simulation relations from concurrent programs to formal specifications. For a formal specification S, a concurrent program P and a simulation relation r from P to S, the proposed technique is outlined as follows: (1) state sequences s0, s1,. .. , sn are generated from P , (2) state sequences s 0 , s 1 ,. .. , s m for S are obtained by converting s0, s1,. .. , sn with r and (3) it is checked that S can accept s 0 , s 1 ,. .. , s m. (1) is very crucial, but we first tackle (2) and (3) and then the present paper focuses on (2) and (3).