Preventing untestedness in data-flow based testing

A large number of path-oriented testing criteria have been proposed in the last twenty years. Surprisingly, almost all of them suffer from a serious weakness, which is called the untestedness syndrome: even though a criterion is satisfied, some statements of the program under test may remain 'untested', i.e., the observed test output does not depend on them. A new data-flow based testing criterion is introduced which does not suffer from untestedness, called the All Program Function (APF) criterion. Intuitively, it requires that each possible computation to every output statement in a program be covered by some test; but for lots of programs APF would require an infinite number of tests. A second, applicable criterion is thus introduced, derived fromAPF and called the Basic Program Function (BPF) criterion. BPF leaves no statement untested and yields finite test suites. Some examples show the application of BPF and investigate the failure-detection capability of the proposed criterion.