TDD - Test Driven Dvelopment | Test First Design

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This presentation introduce to you what is TDD, the RGR concept in TDD and what is the benefits of TDD.
This presentation have been created internally for the Software Team in Hyperlogy

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  • The first rule is straightforward: don’t write code without having a failing automated test because the tests embody the requirements that the code must satisfy, as stated in the Introduction. If there is no requirement (that is, test), there is no need to implement anything. This rule prevents us from implementing functionality that is not tested and not needed in the solution.The second rule states that no code should be duplicated in the program. Code duplication is the epitome of bad software design; it leads to inconsistency problems and a reduced level of confidence in the program over time as people forget where the duplications are. If there is code duplication, it is the programmer’s job to remove it when it is seen. (In Extreme Programming [XP], this rule is called “Once and Only Once!”)
  • Test ListIn Kent Beck’s book, Test-Driven Development: By Example (Addison-Wesley, 2003), he describes a test list. When starting a new task or feature, you need to brainstorm a list of tests. As you think about these tests, write them down. In addition to describing the requirements unambiguously, this test list also indicates the scope of the activity and is the most complete definition of the completion criteria. How long should you spend doing this? For most tasks that end up taking about 4 hours, we spend about 15–20 minutes doing this activity. If the scope of the list is too large, the list can be the basis for further estimation.
  • Test-driven development forces critical analysis and design because the developer cannot create the production code without truly understanding what the desired result should be and how to test it.The software tends to be better designed, that is, loosely coupled and easily maintainable, because the developer is free to make design decisions and refactor at any time with confidence that the software is still working. This confidence is gained by running the tests. The need for a design pattern may emerge, and the code can be changed at that time. The test suite acts as a regression safety net on bugs: If a bug is found, the developer should create a test to reveal the bug and then modify the production code so that the bug goes away and all other tests still pass. On each successive test run, all previous bug fixes are verified.
  • Choosing the First TestThere are differing opinions about which test to choose first. One says that you should choose the simplest test that gets you started and solves a small piece of the problem. Another says that you should choose a test that describes the essence of what you are trying to accomplish. For example, looking at the test list in the previous section, the simplest test is the first one: Create an empty Stack and verify that IsEmpty is true. This operation looks as if it would be easy to implement, but it does not provide a great deal of useful feedback when developing a Stack because the IsEmpty function is a supporting function.
  • TDD - Test Driven Dvelopment | Test First Design

    1. 1. TDD – Test Driven Development Quang Nguyen Ba Software www.hyperlogy.com
    2. 2. Contents What is Test Driven Development (TDD) Red/Green/Refactor Concepts TDD Programming Tasks TDD Benefits .NET Examples TDD Tools www.hyperlogy.com
    3. 3. Test Driven Development Developed by Kend Beck Related to Test First programming concepts of XP Goals – Clean code: no less, no more, no duplicate. – Automated Test – Agile www.hyperlogy.com
    4. 4. 2010 How Agile Are You? survey, www.hyperlogy.com
    5. 5. Test Driven Development TDD Rules – Write new code only if you first have a failing automated test. – Eliminate duplication. Test Types – Programmer Tests: Technical facing or Unit test • Tests are created by developer – Customer Tests: Business facing, acceptance test • Test are created by customer www.hyperlogy.com
    6. 6. Red/Green/Refactor Red – write a little test that doesn’t work, perhaps doesn’t even compile at first Green – make the test work quickly, committing whatever sins necessary in the process Refactor – eliminate all the duplication created in just getting the test to work www.hyperlogy.com
    7. 7. TDD Programming Tasks1. Write the test code.2. Compile the test code. (It should fail because you haven’t implemented anything yet.)3. Implement just enough to compile.4. Run the test and see it fail.5. Implement just enough to make the test pass.6. Run the test and see it pass.7. Refactor for clarity and to eliminate duplication.8. Repeat from the top. www.hyperlogy.com
    8. 8. TDD Benefits The suite of unit tests provides constant feedback that each component is still working. The unit tests act as documentation that cannot go out-of-date When the test passes and the production code is refactored to remove duplication, it is clear that the code is finished, and the developer can move on to a new test. www.hyperlogy.com
    9. 9. TDD Benefits Test-driven development forces critical analysis and design The software tends to be better designed, that is, loosely coupled and easily maintainable Reduced debugging time! Reduced manual testing time Continuous Integration www.hyperlogy.com
    10. 10. TDD Example Unbounded Stack – Push: inserts an element onto the top – Pop: removes the topmost element and returns it – Top: operation returns the topmost element but does not remove it from the Stack – IsEmpty: returns true when there are no elements on the Stack www.hyperlogy.com
    11. 11. Unbounded Stack Test Cases1. Create a Stack and verify that IsEmpty is true.2. Push a single object on the Stack and verify that IsEmpty is false.3. Push a single object, Pop the object, and verify that IsEmpty is true.4. Push a single object, remembering what it is; Pop the object, and verify that the two objects are equal.5. Push three objects, remembering what they are; Pop each one, and verify that they are removed in the correct order.6. Pop a Stack that has no elements.7. Push a single object and then call Top. Verify that IsEmpty is false. www.hyperlogy.com
    12. 12. Unbounded Stack Test List8. Push a single object, remembering what it is; and then call Top. Verify that the object that is returned is the same as the one that was pushed.9. Push multiple objects, remembering what they are; call Top, and verify that the last item pushed is equal to the one returned by Top.10. Push one object and call Top repeatedly, comparing what is returned to what was pushed.11. Call Top on a Stack with no elements.12. Push null onto the Stack and verify that IsEmpty is false.13. Push null onto the Stack, Pop the Stack, and verify that the value returned is null.14. Push null onto the Stack, call Top, and verify that the value returned is null. www.hyperlogy.com
    13. 13. TDD Tools cpputest  NDbUnit csUnit (.Net)  NUnit CUnit  OUnit DUnit (Delphi)  PHPUnit DBFit  PyUnit (Python) DBUnit  SimpleTest DocTest (Python)  TestNG Googletest  TestOoB (Python) HTMLUnit  Test::Unit (Ruby) HTTPUnit  VBUnit JMock  XTUnit JUnit  xUnit.net Moq www.hyperlogy.com
    14. 14. References http://en.wikipedia.org/wiki/Test- driven_development http://www.agiledata.org/essays/tdd.html http://msdn.microsoft.com/en- us/library/aa730844(v=vs.80).aspx http://en.wikipedia.org/wiki/Kent_Beck Test-Driven Development: By Example (Addison- Wesley Professional, 2003), Test-Driven Development in Microsoft .NET by James W. Newkirk and Alexei A. Vorontsov ISBN:0735619484 Microsoft Press © 2004 www.hyperlogy.com
    15. 15. Trân trọng cảm ơn! www.hyperlogy.com www.hyperlogy.com

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