Testing & delivery
Testing, Git, containers, CI/CD, and cloud fundamentals.
The container exits immediately. What should I check?
A container stays running while its main process remains alive. An immediate exit usually means the command finished, failed startup or was killed, rather than that Docker randomly stopped a healthy application. Logs, exit status and runtime configuration tell you which case occurred.
The app cannot reach the database container. What should I check?
Each container has its own network context, so localhost points back to that container rather than a sibling service. Reaching a database requires the correct address, network path, credentials and an accepting database process. Compose startup order can start a process without guaranteeing it has finished initialization.
Tests pass locally but fail in CI. Why?
A local/CI mismatch means the test depends on something that differs between environments. Common differences include runtime versions, installed files, operating-system behavior, time, service availability or test order. Reproducing the CI command in a clean setup exposes these hidden assumptions.
How would I roll back a bad deployment?
Rollback restores a previously working application version after a harmful release. It works only if that version is compatible with the current database, message formats and configuration. A complete rollback plan includes health verification and a way to preserve or reconcile work already performed by the new version.
A cloud API is unreachable. Where do I start?
An unreachable cloud API may fail before the request reaches application code. DNS, TLS, routing, firewall rules, load-balancer health and listening ports are separate layers to verify. Checking them in order avoids opening broad access or restarting healthy services without evidence.
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