Filecmp is a command-line application that gets two filenames as argument and outputs the comparison between them - e.g. if they are the same or not... it may look irrelevant but sometime it's very useful, specially inside scripts.
eXplode is a storage system checker. It contains a generic model checker for real code instead of abstract models. Using this model checker, eXplode can systematically check a storage system against many possible crashes to find crash-recovery errors.