SUMMARYResearch has been conducted on methods of automatically performing tests that focus on the delta (difference) between a revision that is known to function normally in advance and a revision that contains defects to identify the causes of the defects. However, since software had to be created from source programs for each test, an extremely long test time had been required. Also, since the emphasis had only been on the testing tasks and no consideration was given to debugging tasks, these methods were not practical. Therefore, in the current research, the authors propose the DMET debugging technique, which can be used for actual software maintenance. DMET, which reduces the test execution time compared with conventional techniques, supports the entire sequential processing flow from testing to debugging. Also, to verify the effectiveness of the proposed technique, the authors implemented the DSUS development support environment, which uses DMET, and performed comparison experiments. From the results, it was apparent that using DMET enabled the total debugging time to be shortened.