1. Software Engineering 1, CS 355 Unit Testing with JUnit
UWEC Department of Computer Science
Introduction to Object Oriented Programming
Software Engineering 1, CS Unit Testing with JUnit
CS 245

2. Types of Testing Unit testing – test each unit separately
Integration testing – test whole system with units working together
Regression testing – test to make sure additions haven’t broken anything
Others…

3. Focus on Unit Testing
Want to ensure each Java class that we create works as advertised
In past courses, we have primarily tested by creating a “driver” program in the main method of the class
Problems with this approach
tend not to be complete in testing
tend to test at end of coding
testing code integrated with class code
better to have it separate for design reasons

4. JUnit – A Framework for Unit Testing in Java
JUnit - an open-source project to provide a better solution for unit testing in Java
Integrates with many Java IDEs, including Eclipse
Central idea: create a separate Java testing unit (usually a class) for each class you’re creating, then provide a means to easily integrate the testing unit with the tested class for unit testing

5. How JUnit Works Assume class Foo Test class must be named FooTest
append string “Test” at end
Test class must extend (inherit from) junit.framework.TestCase class
e.g.
import junit.framework.TestCase; …
public class FooTest extends TestCase …

6. How JUnit Works (2) Where does the TestCase class come from?
Answer: junit.jar
Must add the junit.jar file to your project Java Build Path if not already present

7. How JUnit Works (3)
One approach: the test class should contain a test method for each named public method in the original class
Note: if multiple constructors, can just have one constructor test method
JUnit does not support testing non-public methods
Each test method should be named in the format: testOriginalMethod, with first lower case letter capitalized
e.g. Foo constructor -> testFoo()
e.g. Foo toString -> testToString()

8. How JUnit Works (4)
How to execute the test class given that there’s no main method?
Execute as a JUnit Test
Run As/JUnit Test
Most environments, including Eclipse, have JUnit plugins or modules to display the results graphically

9. JUnit Simple Example IsoDate class IsoDateTest class IsoDate.java
IsoDateTest.java

10. JUnit Test Case Methods
Note that JUnit uses “assertions”
Assertions are boolean statements that claim that something is true about the code at a particular point
Can test for:
equality
sameness
null-ness
truth or falsehood

11. JUnit Test Case Methods (2)
assertEquals(primitiveExpected, primitiveActual)
assertEquals(objectExpected, objectActual)
assertSame(objectExpected, objectActual)
assertNotSame(objectExpected, objectActual)
assertNull(object)
assertNotNull(object)
assertTrue(boolean condition)
assertFalse(boolean condition)
e.g. assertEquals(0, epoch.getTime());

12. JUnit Test Results Two types of problems when running tests
Failures – an assertion failed
Failure results displayed
Expected and result value displayed in trace
Errors – a problem with the Java code
Try to make sure you have “solid” code, don’t raise any exceptions/errors

13. Value of Testing
In the past, software developers have often put too little energy into testing
Testing frameworks like JUnit make testing easier, allow automation, and make it more likely that your code works correctly
“When the bar is green, your code is clean.” – saying from the JUnit developers
Not always true, but it’s a step in the right direction

14. Test Driven Development
More recent approach
Generated from Agile Software Development processes
Repeat
Develop a test case that meets one requirement (test will of course fail)
Write the code to make that test succeed
Refactor (redesign) the code to ensure good design
Until software is fully developed