How to Test a Regular Expression

Step-by-step

1. Write the smallest pattern that expresses the requirement.
2. Add representative matching examples.
3. Add examples that should not match.
4. Inspect capture groups and boundaries.
5. Test edge cases before using the expression in production.

Test both positive and negative cases

A pattern that matches one desired example can still be too broad. Include realistic inputs that should fail.

Keep complex patterns maintainable

Use clear grouping and avoid unnecessary complexity. If a regular expression becomes difficult to understand, document its intent and test cases.