Regex final check: test near misses as well as matches

A regular expression is not ready because it matches one positive example. Test ordinary valid input, invalid input that looks similar, empty text, multiline text, and Unicode if relevant. Confirm whether the pattern should match the entire string or any substring; anchors and flags matter. Inspect captured groups and replacement output, not just a green match indicator. If the pattern runs on untrusted long text, consider performance and potential backtracking. Record the exact pattern, flags, and representative cases.