Designing Better Software

1. Designing Better Software with Mock Objects using Dependency Injection

2. Who is this guy? greg.hutchinson@fcc-fac.ca

3. Jenga Driven Development (JDD)

4. Jenga Driven Development (JDD)

5. Who are you?

6. What is meant by better software?

7. Easier To Test

8. 100% Coverage (Or at least as close as possible)

9. Looser Coupling

10. Notations

11. NotationIClassName is Interface public interface  ICustomerRepository { ... }

12. Notation  ClassName is Implementation public class CustomerRepository { ... }

13. Client – Refers to a Class that invokes behaviour in another Class Notation Class X (Client) object.doSomething() Class Y public void doSomething() {

14. Testing

15. Tenents of Unit Testing

16. Tenents of Unit Testing

17. Tenents of Unit Testing

18. Dependency Injection

19. What Problem are we solving?

20. Remove Dependency from X to Abc, Def 

21. Dependency Injection

22. Dependency Injection

23. Remove Clutter Other Patterns Introduce public class X {     private IAbc abc;     public void doSomething() {         int x = abc.getValue();  //No error checking/lookup etc.         return x + 42;     } ... } AbcLocator locator = ServiceLocator.locator();  IAbc abc = locator.abc();          or AbcFactory.getAbc();

24. Question? What do we replace these implementations with?

25. Mock Objects

26. EasyMock - Overview

27. EasyMock - Creating Mock Objects Example (Snippet)     ...     IRepository mock = createMock(IRepository.class);

28. EasyMock - Defining Expectations Example (Snippet)     ...     IRepository mock = createMock(IRepository.class);  expect(mock.getValue()).andReturn(42);

29. EasyMock - Change Mode Example (Snippet)     ...     IRepository mock = createMock(IRepository.class);      expect(mock.getValue()).andReturn(42); replay(mock);

30. EasyMock - Manually Inject Mock Example (Snippet)     ...     IRepository mock = createMock(IRepository.class);      expect(mock.getValue()).andReturn(42);     replay(mock); service.setRepository(mock);

31. EasyMock - Invoke Real Method Example (Snippet)     ...     IRepository mock = createMock(IRepository.class);      expect(mock.getValue()).andReturn(42);     replay(mock);     service.setRepository(mock); x = service.doSomething();

32. EasyMock - Assert (verify)  Example (Snippet)     ...     IRepository mock = createMock(IRepository.class);      expect(mock.getValue()).andReturn(42);     replay(mock);     service.setRepository(mock);     x = service.doSomething(); veryify(mock);

33. Question?  How do we know if we have tested everything?

34. Emma - Code Coverage Overview 

35. Emma - Instrumenting Classloader 

36. Emma - Code Coverage Overview 

37. Break

38. Example

39. Example - Terminology CustomerDTO - Data Transfer Object CustomerService - WebService CustomerRepository (Repository Pattern) Customer - Entity (JPA) 

40. Demo

41. Pitfalls? • Each client must provide implementation of Abc to X? • Doesn't this break the concept of encapsulation?

42. Spring IoC Container  a formalized means of composing disparate components into a fully working application ready for use

43. Questions?

44. Thanks Please feel free to contact me at: greg.hutchinson@fcc-fac.ca

45. Two Types of Mock ObjectsImplement your own public class XTest extends TestCase {     public void testDoSomething() {        IAbc mock = new MyMock();        X x = new X();        x.setAbc(mock);        x.doSomething();        assertTrue(x.hasFinished());     } }

46. Two Types of Mock ObjectsImplement your own public class XTest extends TestCase {     public void testDoSomething() {        IAbc mock = new MyMock();        X x = new X();        x.setAbc(mock);        x.doSomething();        assertTrue(x.hasFinished());     } } public class MyMock implements IAbc {     public int getValue() {        return 42; //Answer to life, the universe ...     }     public boolean isValidObject() {         return false;     } }