Testing, Observability, Analytics, and Experimentation
Validation across the lifecycle
Testing as a layered strategy
No single test type can prove a web system is correct. Advanced teams combine unit tests, integration tests, end-to-end tests, accessibility checks, performance monitoring, and production observability to manage risk.
Validation layers
Unit testing
Verifies isolated functions or modules.
Integration testing
Checks interactions between components or services.
End-to-end testing
Simulates user workflows across the system.
Observability
Uses logs, metrics, and traces to understand live behavior.
What each layer is good for
| Layer | Strength | Blind spot |
|---|---|---|
| Unit | Fast logic verification | Does not capture real user flow |
| E2E | Critical-path workflow confidence | Can be slower and brittle |
| Monitoring | Production behavior visibility | May not explain root cause alone |
| A/B testing | Comparative impact measurement | Requires careful experimental design |