You’re pushing code with confidence. The pipeline is green, until it’s not. Suddenly, your CI/CD breaks. But it’s not your code. It’s that one flaky test again. Sound familiar?
Flaky tests in CI (Continuous Integration) are like unreliable coworkers—sometimes they show up, sometimes they don’t. To manage flaky tests, isolate them, investigate root causes, and improve your test design. To eliminate them, remove dependencies, stabilize environments, and refactor tests for reliability.
This blog breaks down how to detect, manage, and eliminate flaky tests, so you can get your pipeline back on track and ensure fast, reliable deployments.
What Are Flaky Tests in CI?
Flaky tests are automated tests that pass or fail inconsistently, even when the underlying code hasn’t changed. They break trust in your test suite, slow down development, and often hide real bugs under false alarms. These tests typically stem from:
- Async timing issues (e.g., race conditions, delayed responses)
- Environment instability (non-deterministic data, slow APIs)
- Shared state or dependencies across test runs
- Poor test isolation or outdated mocking logic
In short, they make teams ignore real failures because they can’t distinguish them from noise.
How You Can Detect Flaky Tests in CI
1. Run Tests Repeatedly
Flaky tests usually reveal themselves through reruns. If a test passes on the second or third try without any changes, it’s likely flaky. Configure your CI tool (GitHub Actions, Jenkins, CircleCI) to rerun failed tests and log the outcomes.
2. Track Test Failures Over Time
Look beyond single build failures and examine test history. Tools like TestRail, Allure, or custom dashboards help spot failure trends. Build a script or use CI plugins to highlight tests that fail intermittently across multiple runs.
3. Log and Analyze Test Metadata
Capture timestamps, system states, and error logs for each test. Flaky tests often fail under certain conditions, like specific OS versions or memory loads, which only show up when logs are reviewed in bulk.
4. Isolate Suspect Tests
Temporarily tag flaky tests (e.g., @flaky) and run them in a separate CI job. This stops them from blocking releases and keeps the main pipelines clean while you fix them.
How to Manage and Eliminate Flaky Tests
1. Quarantine Flaky Tests
Move unreliable tests into a separate quarantine suite. This way, they don’t stop the build while you debug the root cause. Some teams even automate tagging based on failure frequency.
2. Use Retry Logic With Limits
While not a permanent fix, retrying failed tests can help reduce false negatives. Most CI tools let you retry failed steps, but set thresholds—too many retries and you mask the real issue.
3. Refactor Test Code
Stabilize flaky tests by:
- Mocking external APIs
- Avoiding shared test states
- Replacing static waits with dynamic conditions
- Improving assertions and setup logic
Clean, isolated, and well-structured tests are less likely to flake.
4. Stabilize the Environment
Run tests in consistent containers or VMs with controlled data and network behavior. Eliminate randomness in execution by setting fixed seeds or removing time-sensitive operations. Infrastructure as Code (IaC) can help replicate clean, reproducible environments.
5. Implement CI Monitoring
Integrate observability tools like Grafana, Prometheus, or custom dashboards to monitor test reliability. Track flaky test frequency, time to resolution, and impact on deployment. CI analytics help spot and prioritize problem tests.
6. Make Test Reviews Mandatory
Code reviews shouldn’t ignore tests. Enforce test design standards in pull requests, and train devs to identify flaky patterns early, before they reach main branches.
Conclusion:
Flaky tests kill confidence in CI and slow teams down. But with the right mix of tracking, isolation, test refactoring, and observability, you can root them out before they derail your process.
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