Why should you use test driven development? Goals, benefits, principles, guidelines and tools.

1. 13 May, 2008 Test driven development – “If it's worth building, it's worth testing”

2. Why should we use TDD? Because we can't we get the design right from the beginning. Why can't we get the design right from the beginning? Because at the start of the project we have imperfect knowledge about the software we're developing. 13 May, 2008 Test driven development – “If it's worth building, it's worth testing” 2

3. What is TDD? Software development technique Related to the test-first programming concepts of Extreme Programming TDD = TFD + Refactoring 13 May, 2008 3 Test driven development – “If it's worth building, it's worth testing”

4. Goals To have a better code coverage test suite To have specification before validation To write clean code that works But the real benefits are many more than the goals! 13 May, 2008 4 Test driven development – “If it's worth building, it's worth testing”

5. Principles and general guidelines Write new business code only when an automated test has failed When a test fails you have made progress because you now know that you need to resolve the problem TDD does not replace traditional testing, instead it defines a proven way to ensure effective unit testing. If it's worth building, it's worth testing. If it's not worth testing, why are you wasting your time working on it? 13 May, 2008 5 Test driven development – “If it's worth building, it's worth testing”

6. Development cycle I - Steps Create a test: basically just enough code to fail (testing the test) Run the test to ensure that the test does in fact fail (testing the test) Run minimal code necessary to pass the test Refactor the code Clean up Remove duplication Write a new test case …. 13 May, 2008 6 Test driven development – “If it's worth building, it's worth testing”

7. Development cycle II 13 May, 2008 7 Test driven development – “If it's worth building, it's worth testing”

8. Benefits An interesting side effect of TDD: you achieve 100% coverage test You have a short checklist – resolve one piece of functionality at a time Cleaner design than achieved by other methods The design is easier to understand The code becomes easier to work with as the project matures The resulting code is designed for testability 13 May, 2008 8 Test driven development – “If it's worth building, it's worth testing”

9. Benefits – Safety net Every single piece of functionality added will have a test coverage. If anything ever changes, the developer will know right away Better assurance when integrating your code into source control Refactoring becomes a lot easier, so the codebase can be kept always healthy 13 May, 2008 9 Test driven development – “If it's worth building, it's worth testing”

10. Benefits – Usable design Code that you develop through TDD is going to end up looking very different from code you would have written otherwise You don't start with a UML diagram, or a detailed class header file, or anything like that You start by using the feature you're about to implement You're going to be your first user of your code, and you're going to think about how to use it from the beginning 13 May, 2008 10 Test driven development – “If it's worth building, it's worth testing”

11. Benefits - Modularity This is another side effect of having to use the code you're about to write Isolated, modular tests => modular codebase A highly modular codebase will compile much more quickly than one that has grown organically 13 May, 2008 11 Test driven development – “If it's worth building, it's worth testing”

12. Benefits – Documentation builds itself The tests you write while doing TDD are the ideal low-level documentation for your code For every feature, you have at least one example on how to use it correctly and how it's expected to be used. And the best part is that it can't ever get out of date. 13 May, 2008 12 Test driven development – “If it's worth building, it's worth testing”

13. Misconception The unit tests form 100% of your design specification You only need to do unit test TDD is sufficient for testing TDD doesn'tscale Your test suite takes too long to run Not all developers know how to test. Everyone might not be taking a TDD approach. 13 May, 2008 13 Test driven development – “If it's worth building, it's worth testing”

14. Tools Visual Studion Team System Test tools NUnit NCover TestDriven.NET 13 May, 2008 14 Test driven development – “If it's worth building, it's worth testing”

15. Example using NUnit/VS integrated tool Link to VS Solution 13 May, 2008 15 Test driven development – “If it's worth building, it's worth testing”

16. References http://www.developer.com/design/article.php/3622546 http://homepage.mac.com/hey.you/lessons.html http://www.gamesfromwithin.com/articles/0502/000073.html http://msdn2.microsoft.com/en-us/magazine/cc163982.aspx http://www.artima.com/intv/testdriven2.html http://www.parlezuml.com/tutorials/agiledotnet/tdd_nunit.pdf http://en.wikipedia.org/wiki/Test-driven_development 13 May, 2008 16 Test driven development – “If it's worth building, it's worth testing”

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