Hi there! As an app testing guru with over a decade of experience, I‘ve seen my fair share of flaky test cases sabotaging CI pipelines. Let‘s get to the bottom of what causes Cypress tests to flake and fail intermittently.
In this comprehensive guide, you‘ll get insider knowledge on the top causes along with my proven playbook to eradicate those pesky random failures!
What Exactly are Flaky Tests?
Flaky tests seem reliable but fail unpredictably. They exhibit both passing and failing results across runs without any…”
15 Root Causes Behind Flaky Test Failures
Unstable tests might be annoyingly cryptic, but they DO exhibit patterns pointing to underlying issues…
Network Issues
Little hiccups in test environments, third-party services or production APIs can manifest as false alarms. I‘ve seen countless flaky failures thanks to:
- Transient latency spikes or timeout errors
- Loadbalancer failures & Elasticsearch timeout errors
- CDN caching issues returning stale responses
- Upstream API changes not handled properly
For example, a production API alteration slipped in right before a scheduled test run. Despite no frontend changes, a bunch of integration tests checking response schemas suddenly began to fail unpredictably.
Race Conditions
The bane of asynchronous testing! Out-of-order code execution as seen below triggers false test failures:
//Test case pseudo-code
await loginUser()
//Assertion executes before response returns!
expect(page.user).not.toBeNull() Location Differences
Variances between localhost, CI, dev or staging environments bite us:
- Mocked services on local behaving differently
- Production data mismatches from synthetic test data
- Cookie conflicts or missing headers on CI builds
- Upstream bugs lingering only on certain deploys
Strategies to Improve Test Reliability
Let’s move on to a step-by-step game plan to systematically exterminate flaky tests through test hygiene and design patterns…
