domain-model-first

Domain-driven design with a test-first workflow starts by defining the initial domain model, writing a minimal test, and implementing an in-memory repository to validate business rules before infrastructure.

The layered progression for building domain models moves from domain entities and value objects to in-memory repositories, then to use cases, and finally to infrastructure implementation.

Designing aggregates and value objects using TDD involves writing tests for business rules first, then implementing pure domain entities that satisfy those tests without external dependencies.

Use in-memory repositories during domain modeling to test use cases and business logic in isolation, deferring database and infrastructure concerns until the domain model is stable.

Domain-model-first development requires no external frameworks or dependencies, relying on pure TypeScript code to express domain entities, value objects, and aggregates.

Domain models get tangled with infrastructure when repositories are implemented against real databases early; using in-memory repositories first keeps domain logic pure and testable.