1.2The Pipeline as a Safety Net

Think of your pipeline as a series of increasingly rigorous checkpoints. A commit enters from one end and, if it survives every checkpoint, emerges from the other end as a deployable artifact. Each checkpoint catches a different class of problem:

Commit
  |
  v
[Lint & Format]     -- Catches syntax errors, style violations
  |
  v
[Unit Tests]        -- Catches broken logic, regressions
  |
  v
[Integration Tests] -- Catches broken contracts, database issues
  |
  v
[Browser Tests]     -- Catches UI regressions, end-to-end flow failures
  |
  v
[Security Scan]     -- Catches vulnerabilities, dependency issues
  |
  v
[Deploy to Staging] -- Catches environment-specific issues
  |
  v
[Smoke Tests]       -- Catches deployment failures
  |
  v
[Deploy to Production]

Each checkpoint is faster and cheaper to fix than the next one. A lint error caught in 30 seconds costs nothing. A broken API discovered after deployment costs an incident.