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Test Driven Development Introduction


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The simple note introduces the TDD approach

The simple note introduces the TDD approach

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  • 1. Test Driven Development Introduction Issued date: 8/29/2007 Author: Nguyen Phuc Hai
  • 2. Agenda Introduction  Unit test overview  Refactoring  Test Driven Development approach  Q&A 
  • 3. Trainer’s profile Over seven years experienced in software  industry on both product development and out-sourcing. Hand-over various positions from developers,  technical lead, project manager, technical architecture and program/product managers.
  • 4. Trainer’s profile (cont.) Be experienced in managing small, medium  and large projects/program – Took oversight more than 100 associates in one of the biggest account in company Be experienced on technical design,  technical management in various sizes of projects from small to enterprise applications on both desktop and web environment
  • 5. Trainer’s profile Be recognized as an Agile expert that has  experienced in managing Agile process, applying Agile practices. Maintain the blog that share experienced in  software development on both technical and management areas (http://
  • 6. Unit test key ideas
  • 7. Unit test - FAQs Check the link for some common concerns of  applying unit test and its benefits:
  • 8. Unit test best practices Keep test method as simple as possible:  DRY principle (Don’t repeat yourself) – Re-use test set up across test cases: put non- – trivial test data in test set up method Clean test code as productive code – Evident data  All non-trivial methods must be passed unit  test with 100% coverage ratio.
  • 9. Unit test best practices Unit test independent with:  Other unit tests, order of unit test running – Environment (operating system, hardware – configuration, database …) Fix broken test as soon as possible (it should  be immediately) After fixing defect, write unit test to prevent it  re-occur
  • 10. Unit test best practices All test cases must be passed at the end of  working day. Test project code, not library code  Minimal maintenance of test code  If you can not write unit test for some  functionality that means your code has problem! Refactor it immediately
  • 11. How to make code becomes testable Using interface in communication among  layers, modules. Dependency injection  Dependency lookup  Methods/Constructors has as less  parameters as possible (4 is the best number)
  • 12. How to make code becomes testable Class is not depended in many other classes  -> it is hard to initiate instance of this class One method has only one purpose  Be careful with singleton class or static  methods! And the most important: refactoring your  code if it is not testable (esp. legacy code)
  • 13. Refactoring Refactoring is a disciplined technique for  restructuring an existing body of code, altering its internal structure without changing its external behavior. The system is also kept fully working after each small refactoring, reducing the chances that a system can get seriously broken during the restructuring.
  • 14. Refactoring (cont.) Whenever you think you can make more  benefits with your new code: Increase the re-usability – Make the code becomes testable – Avoid the rigid, fragile issues – Better performance – … –
  • 15. Refactoring – best practices Keep small change running before proceed  another change. Unit test should be written to make sure  refactoring does not change system’s behaviors. To legacy system: write test first, refactoring  and verify result
  • 16. Test Driven Development TDD is a technique to improve the quality of  both code and design. Developers will write the test first, then writing the code to make it pass the test. They can refactor code to avoid issues (duplication or non-optimize code …)
  • 17. TDD benefits Promoting high code coverage for productive  code. Improving quality of architecture and code  Prevent defects cost is less than detect  defects cost
  • 18. TDD Cycle Prepare a list of test cases  Follow the TDD Rhythm:  Pick a test to implement – Write a fail test – Quickly make test green – Refactor to eliminate duplication –
  • 19. TDD – Things always do Write test-first  Maintain to-do list  Writing new code only if there is failing  automated test Run all tests all the time not only single  isolated test
  • 20. TDD – Things always do Job is done whenever complete  implementation and all test have green status
  • 21. TDD – Things never do Write test for trivial methods (such as  getters/setters) Commit code with failed test  Big upfront design and code that makes test  first do not cover all cases of writing code
  • 22. TDD best practices Write the simple test first, then write code.  After that write test code for more complexity functionality Run test immediately whenever complete  writing code If spending much time for writing code, break  the functionality into smaller ones and applying TDD for these pieces
  • 23. TDD best practices Whenever test code or productive code  smells, refactor it immediately After writing code, use coverage tool to make  sure productive code is covered 100% by test method. If some piece of code is not covered, your implementation has problem! Use mock objects if needed 
  • 24. Tools support TDD Various tools help developers easier to do  TDD: IDE: Eclipse, MS Visual Studio Team System – Build tools: Ant, Maven, Nant – xUnit tools: Junit, TestNG, DBUnit, Nunit, … – Coverage tools: JCoverage, NCoverage –
  • 25. TDD examples A user story of login page:  Presentation Layer: Login.html, – Service Layer: – Data Access Layer: – More complex user story: applying acegi for  authentication – authorization process: Re-factor – Run test again –
  • 26. TDD examples (cont.) Write the mock up html file: Login.html  Write test class:  Write test method for case user login  success: @Test Public void testLoginSuccess() { …. }
  • 27. TDD examples (cont.) Implement login function that pass the test  Void onSubmit() { if (username.equals(“VietNam”)) { setResponsePage(Helloworld.class); } else { form.error(“Login fail”); } }
  • 28. TDD examples (cont.) Run LoginTest again and verify result (it has  green color) Return the and add feature  verifying user base on database Void onSubmit() { if (userService.getUser(userName) != null) { … } }
  • 29. TDD examples (cont.) The enterprise application that maintains the  suite of test cases and number of test cases is growing daily: Automation unit test – Continuous Integration –
  • 30. TDD examples (cont.)
  • 31. TDD examples (cont.)
  • 32. Q&A Any question of unit test, refactoring and  TDD is welcome 
  • 33. Thank you I hope you enjoy with this course. Any further  discussion, please contact me at Email: – My blog: –