We present a method of generating test cases from the software specifications which are modeled by nondeterministic finite state machines. It is applicable to both nondeterministic and deterministic finite state machines. When applied to deterministic machines, this method yields usually smaller test suites with full fault coverage than the existing methods that also assure full fault coverage. In particular, the proposed mehod can be used to test the control portion of software specified in the formalspecification languages SDL or ESTELLE. We present a method of generating test cases from the software specifications which are modeled by nondeterministic finite state machines. When applied to deterministic machines, this method occurs usually smaller test suites with full fault coverage than the existing methods that also assure full fault coverage. In particular, the proposed mehod can be used to test the control portion of software specified in the formal specification languages ​​SDL or ESTELLE.