Testing Fundamentals

A bug flows New to Assigned to Open to Fixed to Retest to Verified to Closed, with alternate states Reopened, Rejected, Duplicate, Deferred, and Not Reproducible, and you defeat a "cannot reproduce" by handing over exact environment, version, data, steps, logs, video, and a minimal deterministic repro.

Functional testing checks what the system does and non-functional checks how well it does it; put many fast unit tests at the base of the pyramid and few slow end-to-end tests at the top, never the inverted ice-cream cone of mostly manual end-to-end checks.

Severity measures how badly a defect damages the system, priority measures how urgently it must be fixed, and because impact and urgency are different axes a bug can be low-severity high-priority, like a homepage typo, or high-severity low-priority, like a crash in a rarely used admin corner.

Smoke is a wide-but-shallow "is the build alive" gate on every deploy, sanity is a narrow-but-deep check that one change works, and regression is a broad re-run that confirms old behavior still works before release.