Introduction to Unit Tests & TDD

2

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

3

DEFINITION

• Written by developers

• isolate piece of code

• No use of database or external ressources

• Find problems early in dev cycle

4

INITIAL REACTIONS

• Higher quality (less bug)

• Living documentation

• Well-crafted code

• Easier refactoring

• Automatic regression harness

5

BENEFITS

6

HOW UNIT TEST FRAMEWORKS WORK

My Code

My unit test code

Unit test Runner .exe

Unit Test Common Lib

Test Results

Code Coverage

7

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

8

THE TESTS ARE THE SPECS

*.doc files can’t prove software works !

• 100 % code coverage impossible to reach

• Impossible to catch all errors

9

LIMITATION

10

UNIT TEST OR INTEGRATION TEST ?

IT UT

UT

Too often we try to write unmaintainable integration tests

• Isolate data access with an interface

11

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

12

UNIT TEST VS. PROVIDERS

13

TOOLS

14

.NET UNIT TESTING FRAMEWORKS

15

MS TEST TOOLS • Visual studio default interface

• ReSharper

16

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.

17

BEST PRACTICES

18

MORE TEST FIRST TECHNIQUES

• ATDD - Acceptance test driven development

Test written in a business language with a wiki

• BDD

Behavior Driven Development

19

CONCLUSION

Everyone must be involved !

20

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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