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fix-random-ci-test-failure

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Investigate and fix flaky/random CI test failures in dotnet/macios. Trigger on GitHub issues describing intermittent test failures, CI postmortem issues, or when asked to fix a flaky test. Analyzes test code, identifies root causes (shared state, environment dependencies, race conditions), and applies fixes.

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Fix Random CI Test Failure

Investigate and fix flaky CI test failures reported in GitHub issues for dotnet/macios.

When to Use

  • User shares a GitHub issue about a flaky/intermittent test failure
  • Issue has the ci-postmortem label
  • User asks to fix a randomly failing test
  • Test failures appear across unrelated PRs (indicating environment-dependent flakiness)

Workflow

1. Gather Failure Context

Read the GitHub issue to extract:

  • Test name and test suite (e.g., monotouch-test)
  • Error message and assertion failure details
  • Platform (iOS, macOS, tvOS, Mac Catalyst)
  • Affected builds — check if failures span unrelated PRs (confirms flakiness vs. regression)

If build URLs are provided, inspect logs for additional context (stack traces, timing info).

2. Locate and Analyze the Test

Find the test source file:

grep -r "TestMethodName" tests/

Read the full test method and all helper methods it calls. Understand:

  • What external resources does it use? (keychain, file system, network, simulators)
  • Does it use shared/hardcoded identifiers that could collide across parallel runs?
  • Does it properly clean up before and after execution?
  • Are there error paths that silently swallow failures?

3. Identify Root Cause Category

Common flaky test root causes in this repo:

Shared State / Resource Conflicts

  • Symptom: Test uses hardcoded identifiers (e.g., fixed keychain entries, file paths, port numbers)
  • Fix: Use process-unique identifiers (PID, GUID, bundle ID + test name)
  • Reference: tests/monotouch-test/Security/KeyChainTest.cs uses per-process unique IDs

Environment-Dependent State

  • Symptom: Test depends on OS-level state (keychain, permissions, network availability)
  • Fix: Add robust setup/teardown, handle unexpected initial states, add retry logic for transient errors

Unhandled Error Codes

  • Symptom: Code only handles expected success/failure codes, silently fails on unexpected ones
  • Fix: Add fallback handling for unexpected status codes, log diagnostic info

Race Conditions / Timing

  • Symptom: Test passes locally but fails intermittently in CI
  • Fix: Add proper synchronization, increase timeouts, avoid timing-dependent assertions

LAContext / Authentication Issues (Security tests)

  • Symptom: InvalidRecord or authentication-related errors on keychain operations
  • Fix: Only attach LAContext where actually needed (not on plain query/delete operations)

4. Apply the Fix

When fixing:

  1. Prefer unique identifiers over shared ones. Use Process.GetCurrentProcess ().Id, Guid.NewGuid (), or {bundleId}-{testType}-{pid} patterns for resource identifiers.

  2. Create minimal query records. For search/delete operations, don't attach unnecessary attributes (like LAContext) that can cause intermittent errors.

  3. Handle all status codes. Never silently return false for unexpected error codes. Either handle them with a fallback path or fail with a descriptive assertion message.

  4. Add diagnostic logging. Use TestContext.Out.WriteLine to log operation results that would help diagnose future failures.

  5. Clean up legacy state. If renaming identifiers, also clean up entries from old names that may linger on CI agents.

  6. Always clean up in finally blocks. Ensure test resources are released even on failure.

5. If the Fix is Unclear

If you cannot determine the root cause with available information:

  1. Add diagnostic logging to capture operation results (status codes, error details) in future failures.
  2. Log the initial state at test start (e.g., does the resource already exist before the test runs?).
  3. Include all relevant status codes in assertion failure messages.
  4. Explain to the user what additional information the logging will provide and what hypotheses it will help test.

6. Create the PR

  • Branch naming: dev/{username}/fix-{test-name} or similar
  • Commit message should explain all root causes addressed
  • Reference the GitHub issue with Fixes #NNNN if the change actually fixes the problem, or Ref #NNNN if it only adds logging/diagnostics
  • Add the copilot label to the PR

Key Patterns in This Repo

  • Keychain tests in tests/monotouch-test/Security/ are particularly prone to flakiness due to shared macOS keychain state on CI agents
  • InitSecRecord in RecordTest.cs attaches LAContext to all SecRecord instances — this is sometimes unnecessary and can cause InvalidRecord errors
  • KeyChainTest.cs demonstrates the recommended pattern: per-process unique identifiers using bundle ID + test type + PID
  • Tests run on shared CI agent machines where leftover state from previous runs can cause interference