1. Unit testing Java programs Using JUnit
“If it isn't tested, it doesn’t work”
Unit testing Java programs

2. Requirements for tests
Tests must be executable
A test must clearly show whether it executed successfully or not
The not-so-successfully part of the test must not be buried in a pile of test reports.
Unit testing Java programs

3. Which methods should be tested
Test a method if you are not 100% sure that the method is correct.
Methods that usually does not need testing
Simple get and set methods
However, you might call get and set methods in testing other (more complex) methods
Simple toString methods
Unit testing Java programs

4. Unit testing Java programs
Individual test cases
How to write a test case
Extends TestCase
class MyTest extends TestCase { … }
A test method must have the signature
public void testXxx() throws ExceptionsAsYouLike
Generally you would like one test case pr. Java class
The unit to test is a class.
Unit testing Java programs

5. Fixtures: setUp and tearDown
Sometimes you have 2 or more tests that must run on the same data. To ease this JUnit introduces the concept of a “fixture”.
2 methods inherited from TestCase meant to be overridden
setUp()
Executed before each individual test
tearDown()
Executed after each individual test
Unit testing Java programs

6. Unit testing Java programs
Test suites
You get a lot of test cases (1 pr. Java class).
To several test cases at once you define a “test suite”
Make an object of class TestSuite
Add the individual test cases to the TestSuite
Run the TestSuite
Unit testing Java programs

7. Unit testing Java programs
Testing exceptions
Testing an expected exception
try {
method();
fail(“Exception expected”); }
catch (ExpectedException ex) { /* ignore */ }
A test method must have the signature
public void testXxx() throws Exception
That means that you can throw any exception from a test method.
However, if a test methods throws an exception it means that the test has not passed.
Unit testing Java programs

8. Unit testing Java programs
NetBeans assistance
NetBeans can assist you in making TestCases for individual Java class and in assembling the test cases into test suites.
TestCase
Tools → JUnit tests
JUnit generates empty (in fact failing) tests for each public / protected method in a Java class.
Fill you the empty tests and run the test.
Test suites
New → Test Suite
JUnit generates a test suite of all the test cases in the current test package.
Unit testing Java programs

9. Unit testing Java programs
Running tests
JUnit test can be run in several ways
With a graphical user interface
junit.swingui.TestRunner
Uses Swing classes for the GUI
With a textual user interface
Junit.textui.TextRunner
NetBeans uses a textual user interface when you run a test case or suite.
Unit testing Java programs

10. The internal structure of JUnit
JUnit uses the Reflection API
Objects of class Class are submitted to the test suites.
From an object Class JUnit finds all methods named testXxx() and executes those methods.
Calling setUp() before testXxx()
And calling tearDown() after testXxx()
Unit testing Java programs

11. Composite design pattern in JUnit
JUnit uses the composite design pattern to organize individual test cases and test suites
Unit testing Java programs

12. Unit testing Java programs
Testing in XP
Testing is an important discipline in XP (Extreme Programming)
XP idea: Create the test before the code to be tested
Writing the test makes you thing about detailed design
Test is an executable requirements
Writing (and running) test will be a positive experience.
We know when a class is done
When all tests run
Unit testing Java programs

13. Unit testing Java programs
References
Beck & Gamma JUnit Cookbook,
Kent Beck & Erich Gamma invented JUnit
Martin Fowler Refactoring, Addison Wesley 2000
Chapter 4 Building Tests, page
Extreme Programming, Code the Unit Test First
Testing is an important discipline in XP (eXtreme Programming), which is another Kent Bech invention.
Alex Garrett JUnit antipatterns
Unit testing Java programs