211 lines
8.0 KiB
Markdown
211 lines
8.0 KiB
Markdown
---
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name: test-flakiness
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description: "Detect non-deterministic (flaky) tests by reading CI run logs or test result history. Aggregates pass rates per test, identifies intermittent failures, recommends quarantine or fix, and maintains a flaky test registry. Best run during Polish phase or after multiple CI runs."
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argument-hint: "[ci-log-path | scan | registry]"
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user-invocable: true
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allowed-tools: Read, Glob, Grep, Write, Edit, Bash
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---
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# Test Flakiness Detection
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A flaky test is one that sometimes passes and sometimes fails without any code
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change. Flaky tests are worse than no tests in some ways — they train the team
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to ignore red CI runs, masking genuine failures. This skill identifies them,
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explains likely causes, and recommends whether to quarantine or fix each one.
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**Output:** Updated `tests/regression-suite.md` quarantine section + optional
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`production/qa/flakiness-report-[date].md`
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**When to run:**
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- Polish phase (tests have had many runs; statistical signal is reliable)
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- When developers start dismissing CI failures as "probably flaky"
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- After `/regression-suite` identifies quarantined tests that need diagnosis
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---
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## 1. Parse Arguments
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**Modes:**
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- `/test-flakiness [ci-log-path]` — analyse a specific CI run log file
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- `/test-flakiness scan` — scan all available CI logs in `.github/` or
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standard log output directories
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- `/test-flakiness registry` — read existing regression-suite.md quarantine
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section and provide remediation guidance for already-known flaky tests
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- No argument — auto-detect: run `scan` if CI logs are accessible, else
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`registry`
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---
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## 2. Locate CI Log Data
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### Option A — GitHub Actions (preferred)
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Check for test result artifacts:
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```bash
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ls -t .github/ 2>/dev/null
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ls -t test-results/ 2>/dev/null
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```
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For Godot projects: GdUnit4 outputs XML results compatible with JUnit format.
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Check `test-results/` for `.xml` files.
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For Unity projects: game-ci test runner outputs NUnit XML to `test-results/`
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by default.
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For Unreal projects: automation logs go to `Saved/Logs/`. Grep for
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`Result: Success` and `Result: Fail` patterns.
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### Option B — Local log files
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If a path argument is provided, read that file directly.
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### Option C — No log data available
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If no logs found:
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> "No CI log data found. To detect flaky tests, this skill needs test result
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> history from multiple runs. Options:
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> 1. Run the test suite at least 3 times and collect the output logs
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> 2. Check CI pipeline output and save a log to `test-results/`
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> 3. Run `/test-flakiness registry` to review tests already flagged as flaky
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> in `tests/regression-suite.md`"
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Stop and ask the user which option to pursue.
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---
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## 3. Parse Test Results
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For each CI log or result file found, parse:
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**JUnit XML format** (GdUnit4 / Unity):
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- Grep for `<testcase name=` to get test names
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- Grep for `<failure` or `<error` to identify failures
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- Parse `classname` and `name` attributes for full test identifiers
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**Plain text logs**:
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- Grep for pass/fail patterns:
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- Godot: `PASSED` / `FAILED` adjacent to test names
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- Unreal: `Result: Success` / `Result: Fail`
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- Unity: `Test passed` / `Test failed`
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Build a table: `test_id → [run1_result, run2_result, run3_result, ...]`
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---
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## 4. Identify Flaky Tests
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A test is **flaky** if it appears in the result history with both PASS and
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FAIL outcomes across runs with no code changes between them.
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Flakiness thresholds:
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- **High flakiness**: Fails in >25% of runs — quarantine immediately
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- **Moderate flakiness**: Fails in 5–25% of runs — investigate and fix soon
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- **Low/suspected flakiness**: Fails in 1–5% of runs — monitor; may be
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genuinely rare failure
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For each flaky test, classify the likely cause:
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### Cause classification
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| Cause | Symptoms | Fix direction |
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|-------|----------|---------------|
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| **Timing / async** | Fails after awaiting signals or timers; pass rate correlates with system load | Add explicit await/synchronisation; avoid time-based delays |
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| **Order dependency** | Fails when run after specific other tests; passes in isolation | Add proper setup/teardown; ensure test isolation |
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| **Random seed** | Fails intermittently with no pattern; involves RNG | Pass explicit seed; don't use `randf()` in tests |
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| **Resource leak** | Fails more often later in a test run | Fix cleanup in teardown; check orphan nodes (Godot) or object disposal (Unity) |
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| **External state** | Fails when a file, scene, or global exists from a prior test | Isolate test from file system; use in-memory mocks |
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| **Floating point** | Fails on comparisons like `== 0.5` | Use epsilon comparison (`is_equal_approx`, `Assert.AreApproximately`) |
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| **Scene/prefab load race** | Fails when scenes are not yet ready | Await one frame after instantiation; use `await get_tree().process_frame` |
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Use Grep to check the test file for timing calls, randf, global state access,
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or equality comparisons on floats to narrow down the cause.
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---
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## 5. Recommend Action
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For each flaky test:
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**Quarantine (High flakiness):**
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> "Quarantine this test immediately. Disable it in CI by adding
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> `@pytest.mark.skip` / `[Ignore]` / `GdUnitSkip` annotation. Log it in
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> `tests/regression-suite.md` quarantine section. The test is now opt-in only.
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> Fix the root cause before removing quarantine."
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**Investigate and fix soon (Moderate):**
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> "This test is intermittently unreliable. Root cause appears to be [cause].
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> Suggested fix: [specific fix based on cause classification]. Do not quarantine
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> yet — fix the test directly."
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**Monitor (Low/suspected):**
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> "This test shows suspected flakiness. Collect more run data before
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> quarantining. Note it as 'suspected' in the regression suite."
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---
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## 6. Generate Reports
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### In-conversation summary
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```
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## Flakiness Detection Results
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**Runs analysed**: [N]
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**Tests tracked**: [N]
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### Flaky Tests Found
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| Test | System | Fail Rate | Likely Cause | Recommendation |
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|------|--------|-----------|--------------|----------------|
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| [test_name] | [system] | [N]% | Timing | Quarantine + fix async |
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| [test_name] | [system] | [N]% | Float comparison | Fix: use epsilon compare |
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| [test_name] | [system] | [N]% | Order dependency | Investigate teardown |
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### Clean Tests (no flakiness detected)
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[N] tests ran across [N] runs with consistent results — no flakiness detected.
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### Data Limitations
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[Note if fewer than 5 runs were available — fewer runs = less statistical confidence]
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```
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---
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## 7. Update Regression Suite + Optional Report File
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Ask: "May I update the quarantine section of `tests/regression-suite.md`
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with the flaky tests found?"
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If yes: use `Edit` to append entries to the Quarantined Tests table.
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Never remove existing quarantine entries — only add new ones.
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Ask (separately): "May I write a full flakiness report to
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`production/qa/flakiness-report-[date].md`?"
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The full report includes per-test analysis with cause details and
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engine-specific fix snippets.
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After writing:
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- For each quarantined test: "Add the engine-specific skip annotation to
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disable this test in CI. Re-enable after the root cause is fixed."
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- For fix-eligible tests: "The fix for [test] is straightforward —
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change the equality comparison on line [N] to use `is_equal_approx`."
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- Summary: "Once all quarantine annotations are applied, CI should run green.
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Schedule fix work for the [N] quarantined tests before the release gate."
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---
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## Collaborative Protocol
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- **Never delete test files** — quarantine means annotate + list, not remove
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- **Statistical confidence matters** — with < 3 runs, flag findings as
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"suspected" not "confirmed"; ask if more run data is available
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- **Fix is always the goal** — quarantine is temporary; surface the fix
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direction even when recommending quarantine
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- **Ask before writing** — both the regression-suite update and the report
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file require explicit approval. On write: Verdict: **COMPLETE** — flakiness report written. On decline: Verdict: **BLOCKED** — user declined write.
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- **Flakiness in CI is a team problem** — surface the list and recommended
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actions clearly; do not just silently quarantine without the team knowing
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