Flaky tests are a thorn in the side of most software development teams.
Even more so when they have set up an automated CI/CD workflow.
In addition to the security holes they create, flaky tests also lead to the need for manual intervention.
Getting rid of them and cleaning up your test suite should therefore be a priority. Luckily, this article focuses on the different ways of eradicating flakiness in your tests.
Understanding Flaky Tests
Flaky tests are like the chameleons of the testing world, as they change their behavior depending on the context. A test that intermittently fails and passes poses a challenge for developers, who often spend countless hours chasing down false negatives.
These tests lack reliability and consistency, making it difficult to determine the true quality of the software being tested. The variability in test results can stem from a variety of sources, including environmental factors, race conditions, non-deterministic code, or external dependencies.
If you want to know more, take a look at Fabien's article explaining what is a flaky test and how to classify them.
Credit Ilamvazhuthi Mathivanan
Flaky Tests Remediation: Best Practices
Addressing flaky tests requires a proactive approach and continuous effort.
This subject has already been covered by Fabien in his article Flaky Tests: How to Fix Them? If you haven't read it, you should.
In it, he shares with you the best practices to adopt to get rid of your flaky tests:
Split your test suites.
Execute tests on VMs or controlled environments.
Log and document.
Separate and quarantine.
Retry your tests (the good way).
Monitor and alert.
Develop processes of investigations.
Run tests multiple times before merge.
Write and apply good practices.
Without getting too repetitive, here are other best practices you should also keep in mind.
🐞 Debugging and Root Cause Analysis
Invest time in understanding and diagnosing the causes behind flaky tests. Analyze test logs, gather relevant data, and identify patterns or dependencies that may contribute to their instability.
🌍 Test Environment Stability
Ensure that the test environment is consistent and stable. Eliminate external factors that can introduce variability and cause intermittent failures, such as network issues, timing dependencies, or resource constraints.
🎯 Test Isolation and Determinism
Design tests to be independent and deterministic, ensuring they don't rely on external resources or produce different outcomes with the same inputs. Utilize techniques like mocking or stubbing to create controlled and predictable testing environments.
⚙️ Test Retry Mechanisms
Implement retry mechanisms for flaky tests to reduce false positives. By re-running tests that fail intermittently, you can increase the likelihood of obtaining consistent and reliable results.
📊 Test Monitoring and Reporting
Establish a robust test monitoring and reporting system to identify flaky tests in real time. Regularly review test results, track their stability over time, and prioritize their resolution as part of ongoing test maintenance efforts.
You can also take advantage of various tools, such as those from CircleCI, Jetbrains, or CI Monitoring solution from Mergify.
Conclusion
Flaky tests are a real pain in the @$? and they pose a significant challenge in the realm of CI/CD.
Their inconsistent behavior undermines the reliability and efficiency of software engineering teams.
However, by adopting the good practices we've just presented in this article and Flaky Tests: How to Fix Them?, you'll limit the nuisance.
Putting them into practice quickly and regularly will save you a lot of trouble. Problems that are trivial today, but could become major threats tomorrow.