JUnit testing Tutorial Example, from the DevX tutorial linked from the class web page

Code under test: (simplified)
package calc;
public class Calculator {
   private static int result; // Static variable where the result is stored

   public void add(int n) { result = result + n; }
   public void substract(int n)
   {
      result = result - 1; //Bug : should be result = result - n
   }
      public void divide(int n) { result = result / n; }
   public void clear() { // Cleans the result
      result = 0;
   }
   int getResult() { return result;
   }
}
JUnit4 test code: mark tests with annotation @Test, test setup with @Before: 
package junit4;             <--also can put the test in the same package 
import calc.Calculator; 
import org.junit.Before; 
import org.junit.Ignore; 
import org.junit.Test; 
import static org.junit.Assert.*;

public class CalculatorTest {

  private static Calculator calculator = new Calculator();

  @Before
  public void clearCalculator() {
    calculator.clear();
  }

  @Test
  public void add() {
    calculator.add(1); 
    calculator.add(1); 
    assertEquals(calculator.getResult(), 2); 
  }

  @Test
  public void subtract() {
    calculator.add(10); 
    calculator.subtract(2); 
    assertEquals(calculator.getResult(), 8); 
  }

  @Test
  public void divide() {
    calculator.add(8); 
    calculator.divide(2); 
    assert calculator.getResult() == 5; 
  }

  @Test(expected = ArithmeticException.class)
  public void divideByZero() {
    calculator.divide(0); 
  }

  @Ignore("not ready yet")
  @Test
  public void multiply() {
    calculator.add(10); 
    calculator.multiply(10); 
    assertEquals(calculator.getResult(), 100); 
  }
}
Important idea: tests are independent, and all start from a known program state.
That's why above @Before clears the calculator, so nothing is left over from the last test.

Running from the command line: need to enable Java asserts with -ea:

java –ea org.junit.runner.JUnitCore junit4.CalculatorTest
JUnit version 4.1 ...E.EI
There were 2 failures:
1) subtract(junit4.CalculatorTest)
           java.lang.AssertionError: expected:<9> but was:<8> at org.junit.Assert.fail(Assert.java:69)
2) divide(junit4.CalculatorTest)
java.lang.AssertionError at                junit4.CalculatorTest.divide(CalculatorTest.java:40)
FAILURES!!!
Tests run: 4, Failures: 2

Ant integration: Since the DevX tutorial was written, the ant task has been upgraded to JUnit4. Here is the ant task in pizza1. It also works for JUnit3 tests. It just does the above command for you.

     <target name="testDAO1" depends="build">
        <junit fork="yes">
            <formatter type="brief" usefile="false"/>
            <test name="cs636.pizza.dao.PizzaOrderDAOTest1"/>
            <classpath refid="project.classpath"/>
        </junit>
    </target>

Output from this:

testDAO1:
    [junit] Testsuite: cs636.pizza.dao.PizzaOrderDAOTest1
    [junit] Tests run: 2, Failures: 0, Errors: 0, Time elapsed: 0.063 sec
    [junit]
    [junit] ------------- Standard Output ---------------
    [junit] Connecting using driver org.hsqldb.jdbcDriver, connection string jdbc:hsqldb:hsql://localhost/
    [junit] Connecting using driver org.hsqldb.jdbcDriver, connection string jdbc:hsqldb:hsql://localhost/
    [junit] ------------- ---------------- ---------------

Eclipse integration As shown in the demo last week, all you need to do is right-click on the project and select Run as JUnit test, and all tests of the project will be run, showing green bar for success and red bar for failure.

@BeforeClass, @AfterClass: To save time, parts of the setup that need to be done only once can be put in the @BeforeClass.  For us, the original database connection and setup should be done here.

Note that @BeforeClass, @AfterClass must be public and static, unlike @Before, @After, which must be public and non-static.