System tests from unit tests

Large programs have bugs; software engineering practices reduce the number of bugs in deployed systems by relying on a combination of unit tests, to filter out bugs in individual procedures, and system tests, to identify bugs in an integrated system. Our previous work showed how Floyd-Hoare triples, {P}C{Q}, could also be seen as unit tests, i.e. formed a link between verification and test-based validation. A transactional-style implementation allows test post-conditions to refer to values of data structures both before and after test execution. Here we argue that this style of specifications, with a transactional implementation, provide a novel source of system tests. Given a set of unit tests for a system, we can run programs in test mode on real data. Based on an analysis of the unit tests, we intersperse the program’s execution with the preand post-conditions from the test suite to expose bugs or incompletenesses in either the program or the test suite itself. We use the results of these tests, as well as branch-trace coverage information, to identify and report anomalies in the running program.