Intrinsic Properties of Complete Test Suites

Completeness is a desirable property of test suites. Roughly, completeness guarantees that a nonequivalent implementation under test will always be identified. Several approaches proposed sufficient, and sometimes also necessary, conditions on the specification model and on the test suite in order to guarantee completeness. Usually, these approaches impose several restrictions on the specification and on the implementations, such as requiring them to be reduced or complete. Further, test cases are required to be non-blocking — that is, they must run to completion — on both the specification and the implementation models. In this work we deal test cases that can be blocking, we define a new notion that captures completeness, and we characterize test suite completeness in this new scenario. We establish an upper bound on the number of states of implementations beyond which no test suite can be complete, both in the classical sense and in the new scenario with blocking test cases.