DDD Testing Standards

DDD testing requires exhaustive unit tests for domain entities and value objects with 100% coverage mandatory, plus integration tests for critical workflows. Write tests for all business methods, validations, state transitions, edge cases, invariants, and factory methods before implementation using a Test-Driven Development cycle.

Organize tests into layers: unit tests for domain entities and value objects in `tests/unit/domain/entities/`, application layer tests at 95%+ coverage, and integration tests for workflows. Use `*.spec.ts` naming convention and configure coverage thresholds in `jest.config.js` for each layer.

Follow the Red-Green-Refactor cycle: write a failing test for a business method first, implement minimal code to pass the test, then refactor while keeping tests green. This approach produces reliable, well-documented code with comprehensive business logic validation.

Yes. Jest and @nestjs/testing are the testing frameworks for this DDD testing methodology. Integrate coverage enforcement into `jest.config.js` and CI/CD pipelines to enforce strict thresholds across domain, application, and integration layers.

Strict coverage thresholds prevent regressions in critical business logic and ensure all invariants, validations, and state transitions are tested. This rigor is essential in DDD where domain entities and value objects encode core business rules.

Test all business method behaviors, validation rules, state transitions, edge cases, and invariants defined in your domain model. Include factory method testing to ensure entities initialize correctly and satisfy domain constraints.