outside-in-double-loop

To implement a feature with missing dependencies, use an outside-in TDD approach: define the user-facing contract first, stub the unavailable dependencies, pass the outer test, then iteratively build each dependency. This prevents speculative code and ensures tests drive development.

The outside-in double loop approach in TDD is a development process where you write tests for the outer user-facing contract first, then iteratively write inner loops of tests for underlying dependencies. This ensures complex features are built incrementally and strictly driven by test demands.

To build a microservice incrementally with unready downstream services, define the API contract first, stub all internal services, get the API test passing, and then build each downstream service one by one. This ensures development proceeds without waiting for dependencies.

The best way to manage dependencies and avoid premature development is to enforce strict rules about interface definition and dependency construction. Code is only built when a test demands it, ensuring an efficient, driven development process.

You should use an outside-in TDD strategy when implementing features with multiple collaborating modules or services. It is particularly effective when dependencies are not yet available and you need to build complex features incrementally from the user-facing contract down.

No, outside-in TDD does not require existing dependencies before starting. The process guides implementation by starting with the user-facing contract and stubbing downstream services, allowing you to iteratively build dependencies only when tests demand them.