1. A method for testing a data processing system's ability to recover from cache directory errors, said method comprising: storing a directory entry into a cache directory, said directory entry including an address tag and directory parity that is associated with said address tag; storing a cache entry into a cache that is accessed using said cache directory, said cache entry including information and cache parity that is associated with said information; altering said directory parity to imply bad parity, said bad parity implying that said associated address tag is invalid; altering said information to be incorrect, said cache parity indicating good parity, said good parity implying that said information is valid; and testing said data processing system's ability to recover from errors using said directory entry and said cache entry.