Discovering additional violations of Java API invariants

In the absence of formal specifications or test oracles, automating testing is made possible by the fact that a program must satisfy certain requirements set down by the programming language. This work describes Randoop, an automatic unit test generator which checks for invariants specified by the Java API. Randoop is able to detect violations to invariants as specified by the Java API and create error tests that reveal related bugs. Randoop is also able to produce regression tests, meant to be added to regression test suites, that capture expected behavior. We discuss additional extensions that we have made to Randoop which expands its capability for the detection of violation of specified invariants. We also examine an optimization and a heuristic for making the invariant checking process more efficient.