Dependency Injection and Unit Testing in .Net Core

Dependency Injection and Unit Testing in .Net Core

A dive into dependency injection in traditional .Net applications and ASP.Net Core. Followed by how dependency injection enables unit testing in .Net core and EF core. Code examples of how to unit test at the controller, service, and data layers.

Transcript

1. The perfect pair Chris Ayers Dependency Injection & Unit Testing
2. Chris Ayers DevOps Lead @ New Signature Linkedin: /in/chris-l-ayers/ Twitter: @Chris_L_Ayers Projects: https://github.com/Codebytes /UnitTestingDemo https://github.com/Codebytes /DependencyInjectionDemo
3. Topics • Dependency Injection • Why? • SOLID • Design Patterns • Types • Features • DEMO • Unit Testing • Terms • Test Layout and Naming • Mocking • Best Practices • DEMO
4. Why? • Clarity • Maintainability • Reuseability • Modularity • Testability • Use Different Implementations
5. SOLID • Single Responsibility Principle • Open/Closed Principle • Liskov Substituion Principle • Interface Segregation Principle • Dependency Inversion Principle
6. Patterns • Façade • Factory • Strategy • Visitor • Command
7. Façade Pattern Client -complexFacade Façade +ComplexProcess Subsystem 1 +ComplexStep1 Subsystem 2 +ComplexStep2 Subsystem 3 +ComplexStep3 Subsystem 4 +ComplexStep4
8. Factory Pattern Client -shapeFactory <<Interface>> Shape +draw() ShapeFactory +GetShape() : Shape Circle +draw() Square +draw() Triangle +draw() Implements Implements Implements Creates
9. Strategy Pattern <<Interface>> CookingMethod +Cook() Dinner -cookingMethod: CookingMethod Microwave +Cook() ToasterOven +Cook() Oven +Cook() Implements Implements Implements Uses
10. Types of Dependency Injection
11. No Dependency Injection • Not using interfaces to reduce coupling • Hard to test • No clear understanding of relationships between different classes
12. Property Injection • Initialization not guaranteed • Can be good for bigger/complex objects
13. Method Parameter Injection • When a dependency is used for only method and is an edge case
14. Constructor Injection • Clear understanding of dependencies
15. Path to Loosely Coupled Classes Tightly Coupled Classes Implement IoC using Factory Pattern Implement DIP by creating Abstractions Implement Dependency Injection Use IoC Container Loosely Coupled Classes
16. Dependency Injection - Scopes Transient Scoped Singleton
17. Dependency Injection - Features Composition Root Configuration Scopes Factory Support
18. Dependency Injection - Frameworks .Net Core Unity Castle Windsor Ninject AutoFac SimpleInjector Spring.NET StructureMap
19. Dependency Injection - DEMO
20. Resources DEPENDENCY INJECTION IN ASP.NET CORE - HTTPS://BIT.LY/34UR0IB FRAMEWORK-PROVIDED SERVICES - HTTPS://BIT.LY/355G0YV IDISPOSABLE - HTTPS://BIT.LY/2VSH9SJ
21. Decoupling is essential for unit testing. DI is a great way to achieve decoupling. Unit Testing
22. Unit Testing – Terms (SUT) System Under Test or (CUT) Class Under Test Test Doubles Fake Mock Stub Spy Dummy Objects
23. Unit Testing - Architectures • Easy to Test Code • Inversion of Control (IoC) • Interface Segregation • Functional Programming • Hard to Test code • It is tightly coupled to the concrete implementation. • It violates the Single Responsibility Principle. • It lies about its dependencies. • It is hard to understand and maintain.
24. Unit Testing - Layout Split up tests by assembly/project. • Ex: if you have two libraries: foo.dll, bar.dll • have 2 unit test assemblies: foo.tests.dll, bar.tests.dll Try to have at least 1 test class per class • Ex: if you have two classes in project foo: a.cs, b.cs • have 2 unit test classes in project foo.tests: aTests.cs, bTests.cs • If there are a lot of methods, or tests for some methods, split it up if there are a too many tests in one class. Use folders to mirror layout and namespaces of target project
25. Unit Testing - Naming Name test class for the class under test • Foo.cs -> FooTests.cs [UnitOfWork_StateUnderTest_ExpectedBehavior] Examples • public void GetLines_twoLineString_returnsTwoStrings() • public void GetNonWhitespaceLines_null_Throws() • public void ReplaceMultiple_stringWithHashNonMatchingMappings_String() • public void ReplaceMultiple_stringMatchingMappings_UpdatedString()
26. Unit Testing – Frameworks Nunit Xunit MStest
27. Mocking – Frameworks Moq NSubstitute JustMock FakeItEasy
28. Unit Testing – Gotchas Usually only works for Interfaces or Virtual Methods. Statics can be difficult; refactoring can help or Microsoft Fakes Mocking can make assumptions about boundaries
29. Unit Testing – Best Practices AAA Arrange Act Assert One Assert Per Test Method Avoid Test Interdependence Keep It Short, Sweet, and Visible Recognize Test Setup Pain as a Smell Add Them to the Build
30. Unit Testing – What is a good test? Fast Isolated Repeatable Self- Checking Timely
31. Unit Testing - DEMO
32. Questions? I might have answers