introduction to unit tests and tdd

Introduction to Unit Tests & TDD

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UNIT TEST IN AN AGILE CONTEXT

Agile XP UT

A unit test confirms functionality of a small unit of functionality or component

in a larger system

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DEFINITION

• Written by developers

• isolate piece of code

• No use of database or external ressources

• Find problems early in dev cycle

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INITIAL REACTIONS

• Higher quality (less bug)

• Living documentation

• Well-crafted code

• Easier refactoring

• Automatic regression harness

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BENEFITS

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HOW UNIT TEST FRAMEWORKS WORK

My Code

My unit test code

Unit test Runner .exe

Unit Test Common Lib

Test Results

Code Coverage

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TEST DRIVEN DEVELOPMENT

1. Create a falling test Red

2. Make the test pass Green

3. Refactor Improve the internal

implementation without changing the external contract or behavior

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THE TESTS ARE THE SPECS

*.doc files can’t prove software works !

• 100 % code coverage impossible to reach

• Impossible to catch all errors

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LIMITATION

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UNIT TEST OR INTEGRATION TEST ?

IT UT

UT

Too often we try to write unmaintainable integration tests

• Isolate data access with an interface

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UNIT TEST VS. DATA BASE

Critical for teams using third-parties.

• Unit Test to simulate provider calls

• UnitTest unit to send data to providers

If the provider updates its interface test fails

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UNIT TEST VS. PROVIDERS

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TOOLS

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.NET UNIT TESTING FRAMEWORKS

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MS TEST TOOLS • Visual studio default interface

• ReSharper

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MOCKING FRAMEWORK: MOQ

• Test

• Dynamically implement a interface

• New projects have to include unit test

• Legacy code : when a bug is raised, write a UT that fails, fix the bug and the UT is successful.

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BEST PRACTICES

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MORE TEST FIRST TECHNIQUES

• ATDD - Acceptance test driven development

Test written in a business language with a wiki

• BDD

Behavior Driven Development

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CONCLUSION

Everyone must be involved !

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REFERENCES

• http://blog.octo.com/quels-sont-les-types-de-tests-que-l%E2%80%99on-utilise-sur-un-projet-agile/

• http://googletesting.blogspot.fr/

• http://weblogs.asp.net/garrypilkington/archive/2010/02/21/setting-up-ioc-with-mvc-quickly.aspx

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