TDD Architecture Patterns
Software architecture should enable testing, not hinder it. These patterns ensure your system remains decoupled and verifiable.
Core Patterns
1. Hexagonal Architecture (Ports & Adapters)
- Keep your business logic (the Core) isolated from external concerns (DB, UI, APIs).
- Use Ports (interfaces) for the core to communicate with the outside world.
- Use Adapters to implement those ports for specific technologies.
2. Dependency Injection (DI)
- Invert the control of dependencies. Instead of a class creating its helper, it receives it via a constructor or parameter.
- Benefit: Allows you to easily swap real dependencies with mocks in tests.
3. SOLID Principles
- S: Single Responsibility.
- O: Open/Closed (Open for extension, closed for modification).
- L: Liskov Substitution.
- I: Interface Segregation.
- D: Dependency Inversion.
Guidelines
- Avoid Global State: It makes tests non-deterministic and hard to run in parallel.
- Keep Logic Pure: Prefer stateless functions where possible; they are the easiest to test.
- Test-First Design: If a feature is hard to test, it usually means the architecture is too tightly coupled.
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