---
name: fix-flaky-tests
description: Fixes a specific flaky test by analyzing its failure patterns from Tuist, identifying the root cause, and applying a targeted correction. Typically invoked with a Tuist test case URL in the format such as `https://tuist.dev/{account}/{project}/tests/test-cases/{id}`.
---

# Fix Flaky Test

## Quick Start

You'll typically receive a Tuist test case URL or identifier. Follow these steps to investigate and fix it:

1. Run `tuist test case show <id-or-identifier> --json` to get reliability metrics for the test.
2. Run `tuist test case run list Module/Suite/TestCase --flaky --json` to see flaky run patterns.
3. Run `tuist test case run show <run-id> --json` on failing flaky runs to get failure messages and file paths.
4. Read the test source at the reported path and line, identify the flaky pattern, and fix it.
5. Verify by running the test multiple times to confirm it passes consistently.

## Investigation

### 1. Get test case metrics

You can pass either the UUID or the `Module/Suite/TestCase` identifier:

```bash
tuist test case show <id> --json
tuist test case show Module/Suite/TestCase --json
```

Key fields:
- `reliability_rate` — percentage of successful runs (higher is better)
- `flakiness_rate` — percentage of runs marked flaky in the last 30 days
- `total_runs` / `failed_runs` — volume context
- `last_status` — current state

### 2. View flaky run history

```bash
tuist test case run list Module/Suite/TestCase --flaky --json
```

The identifier uses the format `ModuleName/SuiteName/TestCaseName` or `ModuleName/TestCaseName` when there is no suite. This returns only runs that were detected as flaky.

### 3. View full run history

```bash
tuist test case run list Module/Suite/TestCase --json --page-size 20
```

Look for patterns:
- Does it fail on specific branches?
- Does it fail only on CI (`is_ci: true`) or also locally?
- Are failures clustered around specific commits?

### 4. Get failure details

```bash
tuist test case run show <run-id> --json
```

Key fields:
- `failures[].message` — the assertion or error message
- `failures[].path` — source file path
- `failures[].line_number` — exact line of failure
- `failures[].issue_type` — type of issue (assertion_failure, etc.)
- `repetitions` — if present, shows retry behavior (pass/fail sequence)
- `test_run_id` — the broader test run this execution belongs to

## Code Analysis

1. Open the file at `failures[0].path` and go to `failures[0].line_number`.
2. Read the full test function and its setup/teardown.
3. Identify which of the common flaky patterns below applies.
4. Check if the test shares state with other tests in the same suite.

## Common Flaky Patterns

### Timing and async issues
- **Missing waits**: Test checks a result before an async operation completes. Fix: use `await`, expectations with timeouts, or polling.
- **Race conditions**: Multiple concurrent operations access shared state. Fix: synchronize access or use serial queues.
- **Hardcoded timeouts**: `sleep(1)` or fixed delays that are too short on CI. Fix: use condition-based waits instead of fixed delays.

### Shared state
- **Test pollution**: One test modifies global/static state that another test depends on. Fix: reset state in setUp/tearDown or use unique instances per test.
- **Singleton contamination**: Shared singletons carry state between tests. Fix: inject dependencies or reset singletons.
- **File system leftovers**: Tests leave files that affect subsequent runs. Fix: use temporary directories and clean up.

### Environment dependencies
- **Network calls**: Tests hit real services that may be slow or unavailable. Fix: mock network calls.
- **Date/time sensitivity**: Tests depend on current time or timezone. Fix: inject a clock or freeze time.
- **File system paths**: Hardcoded paths that differ between environments. Fix: use relative paths or temp directories.

### Order dependence
- **Implicit ordering**: Test passes only when run after another test that sets up required state. Fix: make each test self-contained.
- **Parallel execution conflicts**: Tests that work in isolation but fail when run concurrently. Fix: use unique resources per test.

## Fix Implementation

After identifying the pattern:

1. Apply the smallest fix that addresses the root cause.
2. Do not refactor unrelated code.
3. If the fix requires a test utility (like a mock or helper), check if one already exists before creating a new one.

## Verification

Run the specific test repeatedly until failure using `xcodebuild`'s built-in repetition support:

```bash
xcodebuild test -workspace <workspace> -scheme <scheme> -only-testing <module>/<suite>/<test> -test-iterations <count> -run-tests-until-failure
```

This runs the test up to `<count>` times and stops at the first failure. Choose the iteration count based on how long the test takes — for fast unit tests use 50–100, for slower integration or acceptance tests use 2–5.

## Done Checklist

- Identified the root cause of flakiness
- Applied a targeted fix
- Verified the test passes consistently (multiple runs)
- Did not introduce new test dependencies or shared state
- Committed the fix with a descriptive message