User:Michael.norman.oracle.com/Info on JUnit4

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Contents

Introduction to JUnit4

  • successor to most widely used unit-testing framework for Java, JUnit3
  • under active development (last JUnit3 release 3.8.2 2006-03-03)
    • JUnit 4 released 2006-02-16
      • 4.1 2006-04-27
      • 4.2 2006-11-16
      • 4.3 2006-11-16
        • 4.3.1 2007-03-28
      • 4.4 (current as of 071204) 2007-07-18

based on Java 5 features

  • no longer need to extend class TestCase
  • test-method names do not have to start with the prefix test
  • mark your test method with a @Test annotation
  • use static import's to get assert methods (instead of via inheritance)
import junit.framework.TestCase;
import org.junit.Test;
import static org.junit.Assert.*;

public class CalculatorTest extends TestCase {

    @Test
    public void testadd() { 
        ....
        assertEquals(4, calculator.add( 1, 3 ));
    } 
}

improved test lifecycle management

  • setUp() and tearDown() replaced with @Before and @After annotations (allows for multiple @Before/@After methods)
public class CalculatorTest {

  @Before
  public void prepareTestData() { ... }

  @Before
  public void setupMocks() { ... }

  @After
  public void cleanupTestData() { ... }
}

improved fixture management

JUnit3:

import junit.framework.*;
import junit.extensions.TestSetup;

public class AllTestsOneTimeSetup {

   public static Connection conn; // database connection

   public static Test suite() {
       TestSuite suite = new TestSuite();
       TestSetup wrapper = new TestSetup(suite) {
           protected void setUp() {
               setUpDatabaseConnection();
           }
           protected void tearDown() {
               tearDownDatabaseConnection();
           }
       };
       return wrapper;
   }

   public static void setUpDatabaseConnection() {
       // one-time initialization code
       conn = ...;
   }

   public static void tearDownDatabaseConnection() {
       // one-time initialization code
       conn.close() ...;
   }
}

JUnit4: multiple @BeforeClass/@AfterClass annotations

import org.junit.AfterClass;
import org.junit.BeforeClass;

public class TestWithDatabaseConnection {

   public static Connection conn; // database connection fixture
   public static Object foo; // another fixture

   @BeforeClass
   public static void setUpDatabaseConnection() {
       conn = ...;
   }

   @BeforeClass
   public static void setUpFoo() {
       foo = ...;
   }

   @AfterClass
   public static void tearDownDatabaseConnection() {
       conn.close() ...;
   }

}

Test Management

  • handle expected exceptions more easily
  • timeouts
  • omit tests

JUnit3 style:

   public void testDivideByZero() {
       boolean worked = false;
       try {
           new Calculator().divide( 4, 0 );
       }
       catch (ArithmeticException e) {
           worked = true;
       }
       assertTrue("did not catch expected exception ", worked);
   }

JUnit4 style:

   @Test(expected=ArithmeticException.class,timeout=5000) // set timeout so that we don't wait too long
   public void divideByZero() {
      new Calculator().divide( 4, 0 );
   }

   @Ignore
   public void notQuiteReady() {
      ...
   }

Multiple Tests

  • suite() method:
public class AllTests extends TestCase {

   public static Test suite() {
       TestSuite suite = new TestSuite();
       suite.addTestSuite(CalculatorTest.class);
       suite.addTestSuite(AnotherTest.class);
       return suite;
   }
  • vs. @SuiteClasses:
@RunWith(value=Suite.class)
@SuiteClasses(value={CalculatorTest.class, AnotherTest.class})
public class AllTests {
 ...
}

Custom Runners

In the previous section, we saw that the suite() was replaced with the @Suite annotation. This is an example of how JUnit4 has been designed to allow for extension and customization. The @RunWith annotation allows for custom behaviour to be implemented before, during or after each test and/or suite is run.

Weaknesses

  • Tools integration
JUnit3 has been integrated into alot of tools (Ant, Eclipse IDE, IDEA, etc). JUnit4 is at a disadvantage because it is new. I have written a special JUnit4 runner for Ant (works in 1.6.5 and 1.7.0) but it is not standard.
  • Reporting
The Ant JUnit3 runner has custom behaviour that allowed the run-output to be customized, generating aesthetically pleasing HTML pages. JUnit4 does not yet have this
  • JDK 5 only