TestableCode

Short demo of designing testable code in .NET Core with interfaces, dependency injection and IoC

Using:

• .NET 6
• Microsoft Dependency Injection
• Moq
• Fluent Assertions
• NUnit

What is testable code?

• Easy to test
• Built from isolated components
• Clean architecture

Advantages of testable code

• Easy to create unit tests
• Usually easier to create other tests as well (UI, integration etc.)
• Readable code
• Self-documenting (unit tests are good documentation)
• Easy to refactor (interchangeable components)
• Reduce fear of change
• Maintainable code

Disadvantages of testable code

• Writing code takes more time
• Increased complexity (more abstraction layers)

Symptoms of not testable code

• “New” keyword (using new on ValueObjects, Dictionaries, Lists is OK).
• Static classes & methods (DateTime, File, Path)
• Framework methods
• Long methods and classes
• Global variables
• Complicated constructors
• Chains of methods (accessing dependencies of dependencies)