Incremental generation of combinatorial test suites starting from existing seed tests

Many researchers have been focusing on building combinatorial test generators having the best possible performances, in terms of smaller test suites and shorter generation times. The majority of tools generates test suites from scratch. This means that when the test suite must be regenerated, the old tests are discarded and a new test suite is built. However, there are many cases in which old test cases, possibly written by hand, need to be (or could be) included in the final test suite, and the test suite completed with new tests in order to reach the desired level of combinatorial coverage. These existing tests that are reused are generally called seed tests. Seed tests could be important for testing domain-specific critical parts of the system, or they could represent old test suites that must be enriched to reach the desired (possibly higher) strength of coverage. In this paper, we propose a new architecture for incremental test generation that starts from existing test seeds. This new architecture is supported by the pMEDICI+ tool which extends our previous effort done for pMEDICI. We evaluate the proposed approach on the benchmarks given in the context of the second edition of the CT-Competition and w.r.t. two application scenarios. For each scenario, we automatically generate seed tests and then we apply pMEDICI+ to obtain the desired test suite. The experiments highlight that using incremental test generation can contribute significantly in the reduction of test generation time and, in many cases, in the reduction of the test suite size.