In testing Nondeterministic Finite State Machines (NFSMs), testing process becomes hypothesis testing, if test sequence repetition numbers are not large enough to satisfy the so-called complete-testing assumption. In this paper, we present a method to determine the repetition numbers of test sequences assuming that each transition is executed with a fixed probability when nondeterministic choice is made. The proposed method ensures the test pass probability of restricted class of faulty machines to be never greater than a given value. Also, we discuss how to select a test suite for NFSMs that guarantees the minimal total test length. (C) 2001 Elsevier Science B.V. All rights reserved.