BEFORE YOU START

A regex that passes one sample can still fail on empty input, Unicode, repeated fields, or a different engine. A small, repeatable test set is more useful than adding syntax until one example matches.

FOLLOW ALONGOpen the live Regex Tester workspace
01

Start with representative lines

Include expected matches, expected non-matches, empty values, and Unicode rather than testing a single happy path.

EXAMPLE
PN-1042 completed
PN-1043 failed
not-an-order
02

Build and name groups

Add one boundary or capture at a time. Named groups make replacement and application code easier to review.

EXAMPLE
(?<id>PN-\d+)\s+(?<status>completed|failed)
03

Inspect every match

Check the full match, capture groups, and offsets. Pay special attention to global and multiline behavior.

EXAMPLE
flags: gmi
04

Preview the replacement

Run the replacement against the test set before applying it to files or database content.

EXAMPLE
$<id> => $<status>
Key takeaways
  • Test failures as deliberately as successes.
  • Regex flavor and flags are part of the expression.
  • Preview destructive replacements first.