How do I test and deploy a Nest app?

Definition:

Testing a Nest application means verifying business rules, framework wiring and real integrations at suitable levels. Deployment then packages that verified application with configuration, health checks and lifecycle handling. Mock-only tests cannot prove the database constraints or authentication chain behave correctly.

Key points:

• Unit-test business rules, integration-test database behavior, and E2E-test key routes.

• Validate config and expose readiness checks before serving traffic.

• Use shutdown hooks to close connections and finish active jobs safely.

• Keep focused E2E cases for validation, denied access and a successful critical flow, not only a health endpoint.

Interview point:

• Distinguish “the image built” from “the deployed app is ready and its important flows work.”