Testing With JUnit

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Testing With JUnit

• Samir Tartir

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What is JUnit

• Open source Java testing framework used to write
  and run repeatable automated tests
• A structure for writing test drivers
• JUnit features include
• Assertions for testing expected results
• Test features for sharing common test data
• Test suites for easily organizing and running
  tests
• Graphical and textual test runners
• JUnit is widely used in industry
• JUnit can be used as stand alone Java programs
  (from the command line) or within an IDE such as
  Eclipse

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What Can JUnit Do?

• JUnit is used to test
• an entire object
• part of an object a method or some interacting
  methods
• interaction between several objects
• A tester class contains more than one test
• Each test is written into one test method
• Test classes include
• A test runner to run the tests (main())
• A collection of test methods
• Methods to set up the state before and update the
  state after each test and before and after all
  tests

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How to Write JUnit Tests

• Need to use the methods of the junit.framework.ass
  ert class
• Each test method checks a condition (assertion)
  and reports back to the test runner whether the
  test failed or succeeded
• All of the methods return void
• A few representative methods of
  junit.framework.assert
• assertTrue (boolean)
• assertTrue (String, boolean)
• assertEquals (Object, Object)
• assertNull (Object)
• Fail (String)

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Sample Assertions

• static void assertEquals (boolean expected,
  boolean actual)
• Asserts that two booleans are equal.
• assertNotNull(java.lang.Object object)
• Asserts that an object isn't null.
• assertNotSame(java.lang.Object unexpected,
  java.lang.Object actual)
• Asserts that two objects do not refer to the
  same object.
• assertTrue(java.lang.String message, boolean
  condition)
• Asserts that the condition is true.
• fail(java.lang.String message)
• Fails a test with the given message.
• For a complete list, see
• http//junit.sourceforge.net/javadoc/org/junit/As
  sert.html

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JUnit Versions

• In JUnit 3.X (Used in the Book)
• import junit.framework.
• extend TestCase.
• name the test methods with a prefix of test
• validate conditions using one of the several
  assert methods
• Explicit use of the setup and tearDown methods
• In JUnit 4.0 and later
• Do not extend from Junit.framework.TestCase
• Do not prefix the test method with test
• No need for explicit use of the setUp and
  tearDown methods
• Use one of the assert methods
• Run the test using JUnit4TestAdapter
• _at_NAME syntax introduced

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Preparing to Test Rectangle

• import JUnit.framework. //
  JUnit stuff
• import JUnit.extensions. //
  JUnit stuff
• import gray.adts.shapes.Rectangle // the class
  to test
• public class RectangleTester extends TestCase
  
• private Rectangle r1, r2 //
  test fixture, objects under test
• / Called AUTOMATICALLY before EACH testXXX()
  method is run. /
• protected void setUp()
• r1 new Rectangle()
• r2 new Rectangle( 2.0, 3.0 )
• / Called AUTOMATICALLY after EACH testXXX()
  method is run. /
• protected void tearDown()
• r1 null
• r2 null

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Sample Test Cases
/ Test Case 2.1 Verify that instantiation was
done properly using default values for the
Rectangles dimensions. / public void
testInstantiateDefault() assertEquals( 1.0,
r1.getLength() ) assertEquals( 1.0,
r1.getHeight() )
/ Test Case 2.6 Verify mutator for length
catches illegal input. / public void
testLengthMutatorIllegal () try
r1.setLength( 0 ) // 0 is illegal exception
should be thrown fail( Should raise
IllegalArgumentException) catch (
IllegalArgumentException e )
assertTrue(true) // expected an exception, so
the test passes
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Additional Resources

• JUnit Javadoc
• http//junit.sourceforge.net/javadoc/
• JUnit Home page www.junit.org