Class 18: Testing with JUnit

Held: Wednesday, 6 October 2004

Summary: Today we consider general issues with unit testing as well as the particulars of the JUnit testing framework.

Related Pages:

• EBoard.
• JUnit.org.
• Some sample code.
• VectorTest.java.

Notes:

• Remember: The world-state groups are to explain why their hash tables worked.
• Extra credit for attending tomorrow's convo (in Harris).
• Yay! Swing maintains much of AWT, but makes it better.
• Questions on the homework?

Overview:

• Writing our own tests.
• Generalizing to a test suite.
• JUnit.

An Exercise: Building a Testing Environment

• We will attempt to engage in XP-like practices (particularly simple design and refactoring) in the construction of a testing environment.
  • We'll act as a very large pair.
  • I will admit that I've thought about a design for a system (and the related design of JUnit). Let's see what evolves.
  • I will also admit that I'm uncomfortable with this evolutionary design.
• First problem: I've created a Point class and want to test the constructor using the getX and getY methods. How do I do so?
• Next problem: I also want to test getAngle and getRadius.
• Next problem: I also want to test the rotate method.
• Next problem: I also want to test the unitVector method.
• Next problem: I also want to test my Polar class.
• Let's see what happens as we code, design, and refactor.

JUnit

• JUnit is a unit testing system for Java.
• That means it is designed to make it easy for you to build and combine tests for individual classes.
• To use JUnit, you must make sure that the collection of classes in on your CLASSPATH. In MathLAN, we use /usr/share/java/junit.jar
• Tests are collected into a single class, which should extend junit.framework.TestCase.
• Each test method should have a name that begins with test.
  • Part of the reason is custom.
  • Part of the reason is to support some automation.
• Each test method has calls to various methods that check results, most typically assert and assertEquals.
• You may also have a method called setUp (note capitalization) which gets called before each test.
• You tell JUnit which tests to run by writing a static zeroary suite method that returns a junit.framework.Test.
• The simplest way to write suite is as follows.

  public static junit.framework.Test suite() {
     return new junit.framework.TestSuite(TestClass.class);
  }
  

• You can also specify which particular methods you want to test.

  public static Test suite() {
     TestSuite suite= new TestSuite();
     suite.addTest(new TestClass("testMethod1"));
     suite.addTest(new TestClass("testMethod2"));
     return suite;
  }
  

• The reading will give you more details.