Test Flakiness

Test Flakiness Detection

A flaky test is one that sometimes passes and sometimes fails without any code change. Flaky tests are worse than no tests in some ways — they train the team to ignore red CI runs, masking genuine failures. This skill identifies them, explains likely causes, and recommends whether to quarantine or fix each one.

Output: Updated tests/regression-suite.md quarantine section + optional production/qa/flakiness-report-[date].md

When to run:

• Polish phase (tests have had many runs; statistical signal is reliable)
• When developers start dismissing CI failures as "probably flaky"
• After /regression-suite identifies quarantined tests that need diagnosis

1. Parse Arguments

Modes:

• /test-flakiness [ci-log-path] — analyse a specific CI run log file
• /test-flakiness scan — scan all available CI logs in .github/ or standard log output directories
• /test-flakiness registry — read existing regression-suite.md quarantine section and provide remediation guidance for already-known flaky tests
• No argument — auto-detect: run scan if CI logs are accessible, else registry

2. Locate CI Log Data

Option A — GitHub Actions (preferred)

Check for test result artifacts:

ls -t .github/ 2>/dev/null
ls -t test-results/ 2>/dev/null

For Godot projects: GdUnit4 outputs XML results compatible with JUnit format. Check test-results/ for .xml files.

For Unity projects: game-ci test runner outputs NUnit XML to test-results/ by default.

For Unreal projects: automation logs go to Saved/Logs/. Grep for Result: Success and Result: Fail patterns.

Option B — Local log files

If a path argument is provided, read that file directly.

Option C — No log data available

If no logs found:

"No CI log data found. To detect flaky tests, this skill needs test result history from multiple runs. Options:

1. Run the test suite at least 3 times and collect the output logs
2. Check CI pipeline output and save a log to test-results/
3. Run /test-flakiness registry to review tests already flagged as flaky in tests/regression-suite.md"

Stop and ask the user which option to pursue.

3. Parse Test Results

For each CI log or result file found, parse:

JUnit XML format (GdUnit4 / Unity):

• Grep for <testcase name= to get test names
• Grep for <failure or <error to identify failures
• Parse classname and name attributes for full test identifiers

Plain text logs:

• Grep for pass/fail patterns:
  • Godot: PASSED / FAILED adjacent to test names
  • Unreal: Result: Success / Result: Fail
  • Unity: Test passed / Test failed

Build a table: test_id → [run1_result, run2_result, run3_result, ...]

4. Identify Flaky Tests

A test is flaky if it appears in the result history with both PASS and FAIL outcomes across runs with no code changes between them.

Flakiness thresholds:

• High flakiness: Fails in >25% of runs — quarantine immediately
• Moderate flakiness: Fails in 5–25% of runs — investigate and fix soon
• Low/suspected flakiness: Fails in 1–5% of runs — monitor; may be genuinely rare failure

For each flaky test, classify the likely cause:

Cause classification

Use Grep to check the test file for timing calls, randf, global state access, or equality comparisons on floats to narrow down the cause.

5. Recommend Action

For each flaky test:

Quarantine (High flakiness):

"Quarantine this test immediately. Disable it in CI by adding @pytest.mark.skip / [Ignore] / GdUnitSkip annotation. Log it in tests/regression-suite.md quarantine section. The test is now opt-in only. Fix the root cause before removing quarantine."

Investigate and fix soon (Moderate):

"This test is intermittently unreliable. Root cause appears to be [cause]. Suggested fix: [specific fix based on cause classification]. Do not quarantine yet — fix the test directly."

Monitor (Low/suspected):

"This test shows suspected flakiness. Collect more run data before quarantining. Note it as 'suspected' in the regression suite."

6. Generate Reports

In-conversation summary

## Flakiness Detection Results

**Runs analysed**: [N]
**Tests tracked**: [N]

### Flaky Tests Found

| Test | System | Fail Rate | Likely Cause | Recommendation |
|------|--------|-----------|--------------|----------------|
| [test_name] | [system] | [N]% | Timing | Quarantine + fix async |
| [test_name] | [system] | [N]% | Float comparison | Fix: use epsilon compare |
| [test_name] | [system] | [N]% | Order dependency | Investigate teardown |

### Clean Tests (no flakiness detected)

[N] tests ran across [N] runs with consistent results — no flakiness detected.

### Data Limitations

[Note if fewer than 5 runs were available — fewer runs = less statistical confidence]

7. Update Regression Suite + Optional Report File

Ask: "May I update the quarantine section of tests/regression-suite.md with the flaky tests found?"

If yes: use Edit to append entries to the Quarantined Tests table. Never remove existing quarantine entries — only add new ones.

Ask (separately): "May I write a full flakiness report to production/qa/flakiness-report-[date].md?"

The full report includes per-test analysis with cause details and engine-specific fix snippets.

After writing:

• For each quarantined test: "Add the engine-specific skip annotation to disable this test in CI. Re-enable after the root cause is fixed."
• For fix-eligible tests: "The fix for [test] is straightforward — change the equality comparison on line [N] to use is_equal_approx."
• Summary: "Once all quarantine annotations are applied, CI should run green. Schedule fix work for the [N] quarantined tests before the release gate."

Collaborative Protocol

• Never delete test files — quarantine means annotate + list, not remove
• Statistical confidence matters — with < 3 runs, flag findings as "suspected" not "confirmed"; ask if more run data is available
• Fix is always the goal — quarantine is temporary; surface the fix direction even when recommending quarantine
• Ask before writing — both the regression-suite update and the report file require explicit approval. On write: Verdict: COMPLETE — flakiness report written. On decline: Verdict: BLOCKED — user declined write.
• Flakiness in CI is a team problem — surface the list and recommended actions clearly; do not just silently quarantine without the team knowing