Clean Architecture & DDD Mastery
1. Architectural Patterns
The Evolution of Architecture: Monolith to Clean Onion Architecture: Dependency Inversion at the core Clean Architecture: The 'Screaming' architecture Hexagonal Architecture (Ports and Adapters)
2. Domain-Driven Design (DDD) Foundations
Ubiquitous Language: Aligning code with business Entities vs Value Objects: Managing identity and state Aggregates & Aggregate Roots: Defining consistency boundaries Bounded Contexts: Handling complexity in large domains
3. Advanced DDD Patterns
Domain Services: When logic doesn't fit in an entity Domain Events: Decoupling side effects via events Repositories: Mediating between domain and data Unit of Work: Ensuring atomic transactions
4. Implementing the Clean Layers
The Domain Layer: Zero dependencies, pure C# The Application Layer: Orchestrating use cases The Infrastructure Layer: Bridging to the outside world The Presentation Layer: Decoupling the UI from logic
5. Patterns for Data & Logic
CQRS (Command Query Responsibility Segregation) MediatR: Implementing the Mediator pattern in .NET Specification Pattern: Encapsulating business rules Policy Pattern: Handling complex authorization rules
6. Enterprise Domain Challenges
Handling Persistence Ignorance with EF Core Mapping Layers: AutoMapper vs Manual Mapping Validation Strategies: FluentValidation in the App Layer Error Handling: Result patterns vs Exceptions
7. Testing Clean Architecture
Unit Testing the Domain: Fast and pure Testing Use Cases with Mocks Integration Testing the Infrastructure ArchUnit .NET: Enforcing architectural rules via tests
8. Real-World Case Study
Refactoring a 'Spaghetti' Monolith to Clean Architecture DDD in Action: Modeling a complex Logistics system
Clean Architecture & DDD Mastery

Unit Testing the Domain: Fast and pure

1 Views Updated 5/4/2026

Pure Logic Testing

Because your Domain layer has zero dependencies, it is the easiest and fastest part of your application to test.

1. Testing Business Rules

You don't need mocks to test a Domain Entity. You just instantiate the class and call its methods. var user = new User(); user.Deactivate(); Assert.False(user.IsActive);. These tests run in milliseconds. You can run 1,000 of them in seconds, giving you near-instant feedback on your business rules.

2. Behavioral Testing

Focus on 'Behavior' rather than 'State'. Test that an entity raises the correct **Domain Event** when a certain condition is met. This ensures that the 'intent' of your domain logic is captured and preserved as the code evolves.

3. Architect Insight

Q: "Should I test my private fields?"

Architect Answer: "NO. Test the public API of your domain. If a business rule requires that a Discount can't be negative, test that passing a negative value to the ApplyDiscount() method throws an error (or returns a failure result). Testing internals makes your tests brittle. Testing behavior makes your architecture robust."

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Clean Architecture & DDD Mastery
1. Architectural Patterns
The Evolution of Architecture: Monolith to Clean Onion Architecture: Dependency Inversion at the core Clean Architecture: The 'Screaming' architecture Hexagonal Architecture (Ports and Adapters)
2. Domain-Driven Design (DDD) Foundations
Ubiquitous Language: Aligning code with business Entities vs Value Objects: Managing identity and state Aggregates & Aggregate Roots: Defining consistency boundaries Bounded Contexts: Handling complexity in large domains
3. Advanced DDD Patterns
Domain Services: When logic doesn't fit in an entity Domain Events: Decoupling side effects via events Repositories: Mediating between domain and data Unit of Work: Ensuring atomic transactions
4. Implementing the Clean Layers
The Domain Layer: Zero dependencies, pure C# The Application Layer: Orchestrating use cases The Infrastructure Layer: Bridging to the outside world The Presentation Layer: Decoupling the UI from logic
5. Patterns for Data & Logic
CQRS (Command Query Responsibility Segregation) MediatR: Implementing the Mediator pattern in .NET Specification Pattern: Encapsulating business rules Policy Pattern: Handling complex authorization rules
6. Enterprise Domain Challenges
Handling Persistence Ignorance with EF Core Mapping Layers: AutoMapper vs Manual Mapping Validation Strategies: FluentValidation in the App Layer Error Handling: Result patterns vs Exceptions
7. Testing Clean Architecture
Unit Testing the Domain: Fast and pure Testing Use Cases with Mocks Integration Testing the Infrastructure ArchUnit .NET: Enforcing architectural rules via tests
8. Real-World Case Study
Refactoring a 'Spaghetti' Monolith to Clean Architecture DDD in Action: Modeling a complex Logistics system