How do you troubleshoot an "Undefined step" error in Cucumber?

An "undefined step" error means Cucumber couldn't find any step definition whose pattern matches a given Gherkin line's text, and it's one of the most common early friction points when writing or modifying feature files.

1. Check the glue configuration - confirm the runner's cucumber.glue setting actually points at the package containing the relevant step definitions; a correct step definition in the wrong (unscanned) package produces exactly this error.
2. Check for typos or subtle wording differences - Cucumber Expressions and regex both require an exact structural match; a step definition written for {string} won't match text using unquoted values, and small wording differences between the feature file and the pattern are a frequent cause.
3. Check parameter type mismatches - a step definition expecting {int} won't match a step passing a non-numeric value in that position.
4. Use Cucumber's snippet suggestion - when a step is genuinely undefined, Cucumber prints a ready-to-use step definition skeleton matching that exact text in its output, which is often the fastest way to confirm exactly what pattern is expected.
5. Check for accidentally duplicated or conflicting glue paths - a misconfigured multi-module project can end up scanning the wrong glue package, or none at all, depending on how paths are set up.

Most undefined-step errors trace back to either a glue configuration issue (the code exists but isn't being scanned) or a genuine mismatch between the feature file's exact wording and the step definition's pattern, rather than a deeper problem with Cucumber itself.