This paper presents a simple method that computes test case coverage information from information on what files were updated to fix a fault found by the test case. It uses a cache to monitor fault-prone files and recommends test cases to rerun to cover updated files. We present an evaluation of the method during two months of development of a large, industrial, embedded, real-time software system. Our results show that the method is effective, reaching weekly cache hit rates in the range 50-80%.