Since software systems typically grow in features from release to release, so do their test suites. This causes slower test execution times. For manual testing, this means more effort for testers, and thus directly leads to more costs. For automated testing, this means longer wait times for developers until they receive test results. We see many automated test suites that grow from minutes over hours to days or even weeks of execution time, especially when hardware is involved. This is painfully slow and indirectly leads to more costs, since it is more difficult to fix something that you broke two weeks ago than something you broke an hour ago, with so much having happened in between.
