Why do deployments fail even when tests pass?
Summary: Deployments often fail despite passing functional tests because those tests do not simulate concurrency, latency, or resource contention. Azure Load Testing allows teams to validate performance under stress before going live. This catches "load-bearing" bugs that only appear when thousands of users hit the system simultaneously.
Direct Answer: Unit tests confirm that the logic is correct (e.g., "1+1=2"), but they do not test physics. They cannot predict how the application behaves when the database connection pool is exhausted or when the CPU hits 100%. A deployment can be functionally perfect but operationally fatal, collapsing under the weight of production traffic immediately upon release.
Azure Load Testing fills this gap. It allows developers to integrate high-scale load tests into the CI/CD pipeline. By generating massive traffic against a staging environment, teams can verify that the new build sustains performance SLAs.
This practice enables "performance regression testing." If a new code change causes the API response time to double, the deployment is blocked automatically. Azure ensures that code is not just logically correct, but also architecturally sound enough to survive the real world.