Quarantine first so the suite is trustworthy again, then fix root causes rather than papering over them with retries. The usual causes are timing and synchronization (fixed sleeps, races), shared or leftover test data, test order dependence, and unstable environments. Fix by waiting on conditions instead of durations, isolating data per test, and making every test independent of execution order.
Why interviewers ask this
Flakiness is the fastest way for a suite to lose its authority, so interviewers want to see that you treat it as a defect rather than as background noise. The answer they want separates quarantine, which is a stopgap, from root cause work, and names concrete causes. Candidates who say just add a retry are telling the interviewer they will happily let real bugs through.
How to structure your answer
- Say that a flaky test is a defect, not noise.
- Quarantine to restore trust, but treat it as temporary.
- Name the common root causes in categories.
- Describe the fixes, especially waiting on conditions not durations.
- Mention tracking flake rate as a metric.
Example answer
First thing I do is stop the bleeding, because a suite that fails randomly gets ignored, and once people ignore it you have no safety net at all. So flaky tests get quarantined into a separate run that does not block the pipeline, with a ticket and an owner, not deleted and not silently retried forever. Then I actually diagnose them. The biggest bucket by far is synchronization: someone used a fixed sleep, or asserted right after a click while the request is still in flight. The fix is waiting on a condition, so the element being interactable or the network call resolving, never a duration. Second bucket is data: two tests using the same account, or a test assuming an empty state the previous run polluted. I fix that by creating data per test with a unique identifier. Third is order dependence, which I flush out by deliberately running the suite in random order. And I track flake rate on a dashboard, because if it is not measured it creeps back. Anything above about one percent I treat as a real problem.
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See how it worksFollow-up questions to expect
- When is a retry actually acceptable?
- How would you find a test that only fails when run after another one?
- What would you do if the flakiness comes from a genuinely unstable environment?
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