Design for testing

Thu 7th March Kevin Jones

Our goal is to produce flexible, maintainable, defect free code.

 

Code:

• Automate the build and deploy process
• Don't leak UI in to domain layers
• Don't leak DB access across layers
• Define new types for each concept even if they are small
• e.g. Money type rather than using a double.
• Build facades
• Amalgamate behaviour in to a new type
• Hide complexity of underlying objects
• Single responsibility principle
• Using concrete types is often a bad idea
• Code to interfaces
• Can replace real objects with test objects
• Can use Dependency Injection
• Use of 'new' means we are tied to an implementation

Test:

• Tests should be isolated
• Unit tests shouldn't use system (file / DB etc.)
• Test names should be descriptive (use the BDD style)
• Given_When_Than()
• e.g. GivenAUserService_WhenIAskForAllUsers_ThenAllUsersAreReturned()
• Arrange -> Act -> Assert

Dependency Injection

• Parameter injection
• Setter injection
• Constructor injection
• Use an IoC container (e.g. Unity / Castle / Ninject / AutoFac for MVC)
• IoC (Inversion of Control) is a principal, Dependency Injection is a consequence of IoC