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-suiteidentifies 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
scanif CI logs are accessible, elseregistry
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/nullFor 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 totest-results/3. Run/test-flakiness registryto review tests already flagged as flaky intests/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
<failureor<errorto identify failures - Parse
classnameandnameattributes 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
| Cause | Symptoms | Fix direction |
|---|---|---|
| Timing / async | Fails after awaiting signals or timers; pass rate correlates with system load | Add explicit await/synchronisation; avoid time-based delays |
| Order dependency | Fails when run after specific other tests; passes in isolation | Add proper setup/teardown; ensure test isolation |
| Random seed | Fails intermittently with no pattern; involves RNG | Pass explicit seed; don't use randf() in tests |
| Resource leak | Fails more often later in a test run | Fix cleanup in teardown; check orphan nodes (Godot) or object disposal (Unity) |
| External state | Fails when a file, scene, or global exists from a prior test | Isolate test from file system; use in-memory mocks |
| Floating point | Fails on comparisons like == 0.5 | Use epsilon comparison (is_equal_approx, Assert.AreApproximately) |
| Scene/prefab load race | Fails when scenes are not yet ready | Await one frame after instantiation; use await get_tree().process_frame |
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]/GdUnitSkipannotation. Log it intests/regression-suite.mdquarantine 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