Troubleshoot Cucumber Scenario Outline Failures

When a Cucumber Scenario Outline fails, the root cause is often a placeholder mismatch or header issue. This guide walks you through a structured diagnostic flow—check placeholder consistency, validate header columns, run a dry‑run, verify encoding, and more—to pinpoint and fix the problem quickly.

Problem Statement

When a Cucumber Scenario Outline fails to run, the most common symptoms are:

Runtime errors such as undefined step or java.lang.IllegalArgumentException: No matching examples found.
Zero scenarios executed in the report, even though the feature file contains valid syntax.
Steps executing with literal placeholder text instead of the data from the Examples table.

Quick Cause–Diagnostic Table

Symptom	Likely Cause	Diagnostic Check
Undefined step errors referencing `<placeholder>`	Placeholder name mismatch	Verify every `<placeholder>` in the step has a matching column in the `Examples` header.
IllegalArgumentException: No matching examples found	Missing or duplicate header columns	Open the feature file and ensure the header row contains unique, non‑empty names.
Steps run with literal `<placeholder>` text	Placeholder omitted from `Examples`	Check that each placeholder appears in the header and every row.
No scenarios executed in the report	Feature file encoding or hidden characters	Open in a UTF‑8 editor and remove any non‑visible characters from the header.
Scenario Outline not picked up in multi‑module build	Incorrect feature file path or @Examples annotation misuse	Confirm the feature file is in `src/test/resources` or configured path.

Ordered Checks and Fixes

Validate Placeholder Consistency
Open the feature file in a plain‑text editor. For every step line that contains <placeholder>, ensure there is a column with the exact same name in the Examples header. Cucumber is case‑sensitive, so <UserName> and <username> are different.

Example:
```
Scenario Outline: Login
  Given the user has a valid username and password
  When they login with username & password
  Then they should see the dashboard

Examples:
  | username | password | dashboard |
  | alice     | secret   | home      |
```
If the header missing dashboard, Cucumber will throw an undefined step error for that placeholder.
Check for Duplicate or Empty Header Columns
Run a quick grep to spot duplicates:
```
grep -oP "(?<=\|).+?(?=\|)" feature.feature | sort | uniq -d
```
Any output indicates duplicate column names. Remove or rename duplicates.
Run a Dry‑Run
Using Maven:
```
mvn test -Dcucumber.options="--dry-run"
```
Or Gradle:
```
./gradlew test -Pcucumber.options="--dry-run"
```
The dry‑run will stop before executing steps, listing any unmatched steps. If the output shows placeholders not replaced, the issue is still in the header/step mapping.
Verify File Encoding
Open the feature file in an editor that shows encoding (e.g., VS Code). Ensure it is UTF‑8 without BOM. Hidden BOM characters can make the first header column invisible to Cucumber, leading to No matching examples found.
Confirm Feature File Path in Build
In a multi‑module project, the test runner might ignore the file if it’s not under src/test/resources or not included in the cucumber.options path. Add an explicit include:
```
mvn test -Dcucumber.options="--features src/test/resources/features"
```
Isolate Parallel Execution Issues
If tests run in parallel, shared mutable Examples data can cause race conditions. Use separate feature files or @ParallelExecution(false) for the problematic outline.
Check Generated Report
After a full run, open the HTML report (e.g., target/cucumber-html-reports/overview.html) and verify that the number of executed scenarios equals the number of rows in the Examples table. A mismatch indicates that some rows were skipped due to earlier failures.

Escalation Criteria

If all above checks pass and the Scenario Outline still fails, consider:

Reviewing the step definitions for parameter types that might reject certain values (e.g., int vs String).
Examining any @Before hooks that could alter the context before the outline runs.
Looking for environment‑specific configuration (e.g., profile‑based Examples tables) that might not be loaded.
Opening a ticket with the Cucumber community or your internal QA team, attaching the feature file, the error logs, and the dry‑run output.

Practical Checklist

All placeholders in steps match header names exactly.
No duplicate or empty header columns.
Feature file is UTF‑8 encoded.
Dry‑run shows no undefined steps.
Test report shows the expected number of executed scenarios.

Conclusion

Scenario Outline failures usually stem from simple placeholder mismatches or header issues. By following the ordered checks above, most problems can be identified and fixed quickly. If the problem persists, the diagnostics guide provides a clear path to escalation and deeper investigation.

Diagnosing and Fixing Cucumber Scenario Outline Failures