Testability and Design Review Questions

Evaluate and improve the testability of system designs, APIs, and architecture. Assess attributes that affect testing such as observability, controllability, isolation, modularity, deterministic behavior, and clear seams for test doubles. Propose design and interface changes that enable reliable unit, integration, and system testing without violating product requirements. Discuss strategies such as dependency inversion, feature flags and test hooks, test harnesses, and observable telemetry to make end to end and integration tests more deterministic, and explain the tradeoffs between improved testability, performance, and maintainability.