Regex Release Checklist
A regular expression that works on one sample can still fail in production. Before shipping a regex, test expected matches, non-matches, boundaries, Unicode behavior, and performance risk.
Write expected matches and non-matches
Keep a small table of values that should pass and fail. Include short, long, empty, malformed, and realistic production-like samples.
Check capture groups
If code depends on groups, verify the group order and optional groups. A small regex edit can shift group numbers and break downstream parsing.
Test boundaries
Check leading and trailing whitespace, punctuation, new lines, tabs, path separators, and repeated delimiters. Boundary bugs are common in validators and log filters.
Consider Unicode and locale
Names, URLs, domains, and text fields may contain non-ASCII characters. Decide whether the regex should accept or reject them, then document that choice.
Review performance risk
Nested repetitions and broad wildcards can cause slow matches on long input. Test with long strings and avoid patterns that can backtrack heavily.
Related tools
Regex Tester helps test matches locally. Use Diff Checker to review regex changes before release.