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

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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

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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.

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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, ...]

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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.

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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."

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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]

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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."

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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