Test Driven Development (TDD) is a software development technique where unit tests are written before functional code to verify functionality. The TDD process follows a "Red, Green, Refactor" cycle where tests fail initially ("Red"), code is written to pass tests ("Green"), and code is refactored to improve design. While TDD may improve code quality and catch errors earlier, studies have shown mixed results on productivity and quality improvements. Adopting TDD fully can be challenging in practice due to issues like incomplete test coverage and resistance to change.

1. Test Driven Development THEORY • FACTS • APPLICATIONS • SUPPORT ALEXEI PIVKINE • YURIY POSLAVSKYY • SWARAJ SHERGILL • QING WEI Group 2

2. Definition and guideline s Applications of TDD Tool support in different programming languages Impact on development time, code quality and maintenance costs Possible issues: theory vs the real world Outline

3. Definition Software Design & Development technique First introduced with Extreme Programming, but recently started gaining more attention on its own Test Driven Development = Test First Development + Refactoring Allows developer to think through the design and understand the requirements before writing the functional code

4. Guidelines The motto of test-driven development is " Red , Green , Refactor." Red : Create a test and make it fail. Green : Make the test pass by any means necessary. Refactor: Change the code to remove duplication in your project and to improve the design while ensuring that all tests still pass. The " Red , Green , Refactor" cycle is repeated very quickly for each new unit of code

5. Test Driven Development Cycle

6. TDD vs. Extreme Programming XP is a deliberate and disciplined approach to software development. XP differs from traditional methodologies primarily in placing a higher value on adaptability than on predictability TDD is an approach to code creation, not a software development methodology TDD first popularized as an aspect of XP TDD and XP are more suitable for small to medium-sized projects

7. Unit Testing A unit is the smallest testable part of an application The goal of unit testing is to isolate each part of the program and show that the individual parts are correct. Available Tools: JUnit for Java CppUnit for C++ NUnit for .NET Test::Unit for Ruby

8. Impact of TDD Microsoft Case Study 1 Team size: 6 Language: C/C++ Experience level: High Location: Collocated Findings

9. Impact of TDD Microsoft Case Study 2 Team size: 5-8 Language: C++/C# Experience level: Medium Location: Collocated Findings

10. Impact of TDD NRC Experiment Developers: 3 rd year undergraduate computer science students Language: Java Experience level: Low Location: Collocated Application Size: Small Results tested using 105 black box tests not available to developers Findings No statistically significant improvements in average code quality More consistent quality results – higher minimum achievable quality Higher productivity due to higher number of produced lines of code (test + product)

11. Impact of TDD Other Case Studies

12. Impact of TDD Requires extra upfront development time Requires more tests per unit of production code Encourages frequent regression testing Improves understanding of underlying requirements May or may not result in significant code quality improvements Note Results are difficult to generalize beyond specific environment

13. Theory vs. Real World Possible Benefits Better structured code Clearly defined interfaces Not afraid to refractor (improve complex code) Possible Pitfalls Faulty tests Incomplete coverage

14. Theory vs. Real World Absence of consistent and reliable data to prove that TDD brings improvements Resistance to change Business pressures Failure to completely embrace the approach

15. Conclusion What is TDD? TDD, XP and unit testing Case studies R eal world issues To TDD or Not to TDD that is the question!

16. References T.Bhat, N.Nagappan. Evaluating the Efficacy of Test-Driven Development: Industrial Case Studies. Available: http://research.microsoft.com/manuvir/papers/isese-fp17288-Bhat.pdf H.Erdogmus. On the Effectiveness of Test-first Approach to Programming. March 2005. Available: http://iit-iti.nrc-cnrc.gc.ca/iit-publications-iti/docs/NRC-47445.pdf Wikipedia, "Test-driven development", Wikipedia , [Online]. Available: http://en.wikipedia.org/wiki/Test-driven_development [Accessed: Feb. 23, 2007]. Agile Data, "Introduction to Test Driven Design (TDD)", Agile Data, [Online]. Available: http://www.agiledata.org/essays/tdd.html [Accessed: Feb. 23, 2007]. F Geisendörfer, "Test Driven Development in Real World Apps," September 10, 2006. [Online]. Available: http://www.thinkingphp.org/2006/09/10/test-driven-development-in-real-world-apps/ . [Accessed Feb. 23, 2007]. L. Wyssocky, "Some Pitfalls of Test Drive Development," March 25, 2006. [Online]. Available: http://blog.qualityaspect.com/2006/03/25/some-pitfalls-of-test-driven-development/. [Accessed Feb. 23, 2007]. "TDD viewpoint," January 16, 2005. [Online]. Available: http://neilthespod.spaces.live.com/blog/cns!F11ED9853AA5674B!110.entry. [Accessed Feb. 23, 2007]. Unit Testing [Online] Available: http://en.wikipedia.org/wiki/Unit_testing [Accessed February 23, 2007] JUnit Framework [Online] Available: http://www.junit.org [Accessed February 23, 2007] CppUnit Framework [Online] Available: http://cppunit.sourceforge.net/cppunit-wiki [Accessed February 23, 2007] NUnit Framework [Online] Available: http://www.nunit.org/ [Accessed February 23, 2007] Ruby Test::Unit [Online] Available: http://www.ruby-doc.org/stdlib/libdoc/test/unit/rdoc/classes/Test/Unit.html [Accessed February 23, 2007] What is Extreme Programming [Online] Available: http://www.extremeprogramming.org/what.html [Accessed February 23, 2007] Jeffrey Palermo, “Guidelines for Test-Driven Development”, Visual Studio 2005 Technical Articles, May 2006 , [Online] Available: http://msdn2.microsoft.com/en-us/library/aa730844(VS.80).aspx [Accessed: Feb. 23, 2007].