This document provides tips and best practices for unit testing code. It discusses why unit testing is important, such as guarding against bugs and enabling refactoring. It also covers different types of testing and recommends a test-first approach using test-driven development. Specific tips include breaking dependencies through dependency injection, using fakes/mocks to replace external dependencies, and following principles like single responsibility to make code more testable.

1. Unit Testing Practical Tips

2. In the beginning First testing experience

3. Why Unit Testing? Instead of starting by Testing Manually, you start by testing programmatically. You test the code once… … and then continuously afterwards. Guards against others breaking your code. Guards against regression errors. Refactoring Ruthlessly Peace of Mind

4. Types of Testing – All Important Functional Testing (manual) Integration Testing (automated) (Dosens) Slow Unit Testing (automated) (Hundreds) Localize Failures Fast Dynamic Language Debuggers UI Layer Person View Person Controller Person Model Logic Layer Security Manager Data Layer

5. Test-First of Test-After? The difference is only When you write your tests? Test-After is painful and boring. Test-First makes unit testing easier. Unit Testing == Good. Win win situation. Test-Driven-Design Test-First drives the Design – Low Coupling. Write only enough to make the test pass. YAGNI

6. Automatic Test Generation? Only possible after the code has been written. You won’t get tests like… Test_that_user_registration_fails_on_invalid_ID() Doesn’t test Intent, can only test Methods.

7. Why testing efforts fail When tests become frustrating Integration Tests != Unit Tests Slow Brittle – break unnecessarily Hard to Write due to highly coupled code.

8. Let’s test some code

9. What to test? Single Responsibility Principle Test the responsibility of the Controller Action. ApplicationSuccess view should be returned if application succeeds. ApplicationFailure view should be returned with a reason if application fails.

10. Our “Unit Test” Database Web Service Session State

13. Injecting Fakes ControllerTest Tests… Creates… Fake DB Repo Controller Uses… Fake DB Repo

14. Step 2: Fake object and Dependency Injection

15. Step 2: Fake object and dependency injection

17. Specify expectations

19. Step 3: Abstract and Mock Session

20. Tips

21. Tip: A handy private class

22. Tip Fine grained is better 100 tests that test 100 things is better … than 10 tests that test a 100 things. Execute the same action many times in different tests and verify different results in each call. Makes errors easier to isolate.

23. Tips Break Dependencies – strive for low coupling Use Dependency Injection Avoid public Statics Avoid Singletons Use Interfaces to abstract calls to other classes Use Mocks to mimic and test behaviour Single Responsibility Principle – break things into smaller classes and test independently.

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