A regular expression is easier to maintain when you test it against both expected matches and near-misses. The goal is not only to find a match, but to make the match boundaries and assumptions clear.
Start with representative cases
Create examples that should match, examples that should not match, and edge cases such as empty strings, Unicode characters, line breaks, and unexpected punctuation.
Inspect groups and flags
Use capture groups when you need to extract parts of a match. Test flags such as case-insensitive, multiline, and global matching deliberately because they can change the result without changing the pattern itself.
Prefer a simpler pattern
A shorter expression with explicit boundaries is usually easier to review than a clever pattern with many nested alternatives. Keep the test examples near the code that uses the expression.