Top 3 Regression Interview Questions

Browse 3 real-world technical and behavioral interview questions about Regression. Review scenarios, edge cases, and architectural best practices.

CPU saturates on every node minutes after a release that contained forty commits. How do you find the cause?

Stop the bleeding first by rolling back or disabling the suspect path, then find the cause by profiling the saturated process rather than by reading the diff, because a profile names the hot function directly while forty commits offer forty plausible stories. Use this performance analysis answer to show the decision, trade-off, and evidence rather than a memorised definition.

hardscenario

A test that has passed for a year starts failing after a refactor that was supposed to change nothing. Is it a bug or a bad test?

Work out what the test was actually asserting. If it pins behaviour a user depends on, the refactor changed behaviour and the test did its job; if it pins an implementation detail, it never had value and the failure is the cost of having written it that way.

mediumconcept

Every test passed and the release broke in production anyway. How do you work out what your suite was never going to catch?

Reconstruct the defect's exact path, then ask at which layer a test could have seen it and why none did, distinguishing a missing case from a whole condition your environments cannot reproduce, and fix the class rather than adding one test for this instance.

hardscenario