IME, one of the places hyrums law shows up the most is in tests. I've seen tests of various types (unit, integration end-to-end) break because they made assump

IME, one of the places hyrums law shows up the most is in tests. I've seen tests of various types (unit, integration end-to-end) break because they made assumptions about behaviors that weren't garanteed, and supposedly backwards compatible updates broke them. Here are some examples of things that have broken tests: - an update resulted in a change in the order of elements in a Hashmap or set. - a change in an error message (or other user-facing message), changed - a change in how leap days are handled for datetime arithmetic - change in the format of locale-specific datetimes - the timezone offset for a given area - removal of internal-only APIs that were accessed using reflection - something performed faster, which revealed race conditions in the testing code - changing the precise representation of some data format. To give a specific example, changing a single byte when gzip compressing a file, that has no impact on the compressed content.