Faster tests run earlier, slower tests run later. Unit tests block the commit; E2E tests block the deploy. Never let a slow test suite slow down every developer's commit.
Strong answers describe a test pyramid in the pipeline: unit tests on every commit (fast, fail fast), integration tests on PR merge, E2E/smoke tests on staging deployment, and canary/synthetic monitoring in production. Best candidates discuss balancing speed with coverage and handling flaky tests in CI.
Tests DevOps awareness. QA engineers who understand CI/CD can design test strategies that enable fast delivery rather than blocking it. Ask: "What do you do when a test suite takes too long to run in CI?"