Clean Architecture Best Practices

Comprehensive guide to Clean Architecture principles for designing maintainable, testable software systems. Based on Robert C. Martin's "Clean Architecture: A Craftsman's Guide to Software Structure and Design." Contains 42 rules across 8 categories, prioritized by architectural impact.

When to Apply

Reference these guidelines when:

• Designing new software systems or modules
• Structuring dependencies between layers
• Defining boundaries between business logic and infrastructure
• Reviewing code for architectural violations
• Refactoring coupled systems toward cleaner structure

Rule Categories by Priority

dep-

entity-

usecase-

comp-

bound-

adapt-

frame-

test-

Quick Reference

1. Dependency Direction (CRITICAL)

• dep-inward-only

  - Source dependencies point inward only

• dep-interface-ownership

  - Interfaces belong to clients not implementers

• dep-no-framework-imports

  - Avoid framework imports in inner layers

• dep-data-crossing-boundaries

  - Use simple data structures across boundaries

• dep-acyclic-dependencies

  - Eliminate cyclic dependencies between components

• dep-stable-abstractions

  - Depend on stable abstractions not volatile concretions

2. Entity Design (CRITICAL)

• entity-pure-business-rules

  - Entities contain only enterprise business rules

• entity-no-persistence-awareness

  - Entities must not know how they are persisted

• entity-encapsulate-invariants

  - Encapsulate business invariants within entities

• entity-value-objects

  - Use value objects for domain concepts

• entity-rich-not-anemic

  - Build rich domain models not anemic data structures

3. Use Case Isolation (HIGH)

• usecase-single-responsibility

  - Each use case has one reason to change

• usecase-input-output-ports

  - Define input and output ports for use cases

• usecase-orchestrates-not-implements

  - Use cases orchestrate entities not implement business rules

• usecase-no-presentation-logic

  - Use cases must not contain presentation logic

• usecase-explicit-dependencies

  - Declare all dependencies explicitly in constructor

• usecase-transaction-boundary

  - Use case defines the transaction boundary

4. Component Cohesion (HIGH)

• comp-screaming-architecture

  - Structure should scream the domain not the framework

• comp-common-closure

  - Group classes that change together

• comp-common-reuse

  - Avoid forcing clients to depend on unused code

• comp-reuse-release-equivalence

  - Release components as cohesive units

• comp-stable-dependencies

  - Depend in the direction of stability

5. Boundary Definition (MEDIUM-HIGH)

• bound-humble-object

  - Use humble objects at architectural boundaries

• bound-partial-boundaries

  - Use partial boundaries when full separation is premature

• bound-boundary-cost-awareness

  - Weigh boundary cost against ignorance cost

• bound-main-component

  - Treat main as a plugin to the application

• bound-defer-decisions

  - Defer framework and database decisions

• bound-service-internal-architecture

  - Services must have internal clean architecture

6. Interface Adapters (MEDIUM)

• adapt-controller-thin

  - Keep controllers thin

• adapt-presenter-formats

  - Presenters format data for the view

• adapt-gateway-abstraction

  - Gateways hide external system details

• adapt-mapper-translation

  - Use mappers to translate between layers

• adapt-anti-corruption-layer

  - Build anti-corruption layers for external systems

7. Framework Isolation (MEDIUM)

• frame-domain-purity

  - Domain layer has zero framework dependencies

• frame-orm-in-infrastructure

  - Keep ORM usage in infrastructure layer

• frame-web-in-infrastructure

  - Web framework concerns stay in interface layer

• frame-di-container-edge

  - Dependency injection containers live at the edge

• frame-logging-abstraction

  - Abstract logging behind domain interfaces

8. Testing Architecture (LOW-MEDIUM)

• test-tests-are-architecture

  - Tests are part of the system architecture

• test-testable-design

  - Design for testability from the start

• test-layer-isolation

  - Test each layer in isolation

• test-boundary-verification

  - Verify architectural boundaries with tests

How to Use

Read individual reference files for detailed explanations and code examples:

• Section definitions - Category structure and impact levels
• Rule template - Template for adding new rules

Reference Files