4.2CI/CD and containers

What DevNet asks is not the definition of "what CI/CD is" but whether you can read what the pipeline or Dockerfile in front of you guarantees and where it is flawed. A pipeline that deploys without passing tests mass-produces incidents, a Dockerfile that ignores caching needlessly slows builds, and an image missing CMD will not start. This section covers CI/CD stages, Python unit tests, and each Dockerfile instruction from the viewpoint of reading and diagnosing a presented artifact.

4.2.1The CI/CD pipeline

• CI (continuous integration) integrates developers' changes into a shared branch frequently, running an automated build and test each time to catch breakage early. CD (continuous delivery/deployment) advances an artifact that passed tests all the way to automatic release/production. In short, it makes build -> test -> deploy repeatable without human hands.
• The heart of a pipeline is a gate: do not advance if tests fail. It is correct design that if the test stage is red, deploy does not run; a pipeline that skips tests and pushes to production is an automated incident. The earlier and smaller the failure is caught, the cheaper the fix.