2 Unit Testing

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Introduction to Unit Testing

SE 2 Tutorial

Herman Lee

May 26, 2008

Based on tutorial slides prepared by Thiago Bartolomei

SE 3 lecture slides prepared by Paulo Alencar



Testing Stages Unit testing

Testing of individual components

Integration testing

Testing to expose problems arising from the combinationof components

System testing

Testing the complete system prior to delivery

Acceptance testing

Testing by users to check that the system satisfies

requirements. Sometimes called alpha testing



Approaches to Low Level Testing

Debugging/Output calls

Cannot be automated

Time consuming

Application and test code get tangled (output calls) Unit testing

Set of test cases targeting a single module and

organized in test suites

Strongly encouraged by the agile community



More Reasons to do Unit Testing Provide a working specification of the

functional code

Automation

Write test once, use many times

Regression tests – incorrect changes discovered

immediately – more confidence in the code



Test Driven Design (TDD)

TDD = Test First Development + Refactoring



Test First Development “The act of writing a unit test is more an act of design

than of verification. It is also more an act of documentation than of verification.” (Robert C. Martin)

Idea is to write first the unit tests for a module, andthen implement the module. Why?

Writing the test makes you understand better the functional

code and thus design it better (from the client perspective) Test becomes a documentation artifact, that clearly states the

intention of the module



Test Driven Design Steps

Write tests that fail

Implement modules to make

tests passRun all tests to make sure

nothing is brokenRefactor to keep code clean

Continue development





Preparing Eclipse Project Create a regular project

Project properties

Build Path–

add JUnit as a library (alreadyshipped with Eclipse) Build Path – optionally add a folder for tests

Compiler – if JUnit version 4, use Java version 5

That's it!



Example 1–

Test Case (JUnit 3) 1) Test class must subclass TestCase. Usually it is

named by adding suffix “Test” to tested class name.

2) Test methods must have prefix “test”

3) assertTrue(), assertEquals(), etc, give

test pass conditions. E.g. assertTrue(x==10);

4) Test fixture – a common environment to run a set of similar tests. Use setUp() and tearDown()

methods to create and destroy the environment





JUnit 4 Test Cases

No longer have to extend TestCase

Test methods annotated with @org.junit.Test

setUp/tearDown annotated with @Before/@After Assertions statically accessed from Assert

Test Suites

No longer extend TestSuite

Annotated with RunWith and Suite



Example

Source:

http://www.devx.com/Java/Article/31983/0/page/1



JUnit 3

vs. JUnit 4

Source:

http://www.devx.com/Java/Article/31983/0/page/2



DEMO in Eclipse







Some problems you may encounter “Where do I put my tests?”

Either in the same package as the tested class:

pack.TheClass, pack.TheClassTest

Or in a test package:

pack.TheClass, pack.test.TheClassTest

Also, in an Eclipse project, you can have differentsource folders with the same package:

src/pack.TheClass,

test/pack.TheClassTest

Advantage – you have protected access to the class



Some problems you may encounter How to test UI?

Test functionality by accessing directly the lower

tier (maybe a Facade or MVC pattern?) Testing UI itself usually requires specific tool

support - Ex. HTTPUnit to do webpages testing



References / Further Study Test Driven Development (TDD)

Test Driven Development: By Example, by Kent Beck

http://www.agiledata.org/essays/tdd.html

Agile Software Development, Refactoring, Test FirstDesign

Agile Software Development: Principles, Patterns, and

Practices, by Robert C. Martin

Refactoring: Improving Design of Existing Code, by

Martin Fowler

http://www.xprogramming.com and .org



References / Further Study Unit test design patterns

http://www.marcclifton.com/tabid/87/Default.aspx

http://www-106.ibm.com/developerworks/library/j-

mocktest.html

JUnit

http://www.junit.org

JUnit 3 vs 4

http://www.devx.com/Java/Article/31983

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