fix-flaky-tests

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Translated

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}`.

2installs

Sourcetuist/agent-skills

Added on2026-02-13

NPX Install

npx skill4agent add tuist/agent-skills fix-flaky-tests

SKILL.md Content

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Fix Flaky Test

Quick Start

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

Run

tuist test case show <id-or-identifier> --json

to get reliability metrics for the test.

Run

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

to see flaky run patterns.

Run
```
tuist test case run show <run-id> --json
```
on failing flaky runs to get failure messages and file paths.
Read the test source at the reported path and line, identify the flaky pattern, and fix it.
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

Open the file at
```
failures[0].path
```
and go to
```
failures[0].line_number
```
.
Read the full test function and its setup/teardown.
Identify which of the common flaky patterns below applies.
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:

Apply the smallest fix that addresses the root cause.
Do not refactor unrelated code.
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

fix-flaky-tests

NPX Install

Tags

SKILL.md Content

Fix Flaky Test

Quick Start

Investigation

1. Get test case metrics

2. View flaky run history

3. View full run history

4. Get failure details

Code Analysis

Common Flaky Patterns

Timing and async issues

Shared state

Environment dependencies

Order dependence

Fix Implementation

Verification

Done Checklist