Test Driven Development (TDD) is a software development process that relies on the repetition of short development cycles called "red-green-refactor" cycles. Each cycle begins with writing an automated test that defines a new function or improves an existing function. The test is then run to verify it fails ("red"). Code is then written to implement the new function or change ("green"). Finally, code is refactored to improve design and readability without changing functionality. TDD results in code that is well-tested, loosely coupled, and easy to maintain or modify. Popular TDD tools include JUnit, NUnit, and PHPUnit.

1. TDD – Test Driven Development
Quang Nguyen Ba
Software
www.hyperlogy.com

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. 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. 2010 How Agile Are You? survey,
www.hyperlogy.com

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. 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. TDD Programming Tasks
1. 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. 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cannot go out-of-date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. 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. 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. Unbounded Stack Test Cases
1. 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. Unbounded Stack Test List
8. 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. 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. 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. Trân trọng cảm ơn!
www.hyperlogy.com
www.hyperlogy.com