Tutorial

The following is based on an understanding JUnit. In case your are not familiar with JUnit please check the following JUnit Tutorial .

Download EasyMock from the EasyMock Homepage and add the easymock.jar to your classpath. You also need to download Objenesis and Cglib and add there jars to your classpath.

Create a new Java Project JavaMockTest. Create the following classes. The class IncomeCalculator should be tested. The class has the purpose to calculate based on the provided method and position the salary of a person. Obviously the test depends on the provided methods.

			
package income;

public enum Position {
	BOSS, PROGRAMMER, SURFER
}

		

			
package income.exceptions;

public class PositionException extends RuntimeException {

	private static final long serialVersionUID = 1L;

	public PositionException(String message) {
		super(message);
	}
}

		

			
package income.exceptions;

public class CalcMethodException extends RuntimeException {

	private static final long serialVersionUID = 1L;

	public CalcMethodException(String message) {
		super(message);
	}
}

		

			
package income.method;

import income.Position;

public interface ICalcMethod {

	public abstract double calc(Position position);

}
		

			
package income;

import income.exceptions.CalcMethodException;
import income.exceptions.PositionException;
import income.method.ICalcMethod;


public class IncomeCalculator{
	
	private ICalcMethod calcMethod;
	private Position position;

	public void setCalcMethod(ICalcMethod calcMethod){
		this.calcMethod = calcMethod;
	}
	public void setPosition(Position position){
		this.position = position;
	}
	public double calc (){
		if (calcMethod==null){
			throw new CalcMethodException("CalcMethod not yet maintained");
		}
		if (position==null){
			throw new PositionException("Position not yet maintained");
		}
		return calcMethod.calc(position);
	}
}

		

Using Eclipse JUnit functionality create a new test for IncomeCalulator. In my example I did also create a new source folder "test" before in which I place the test classes.

Here is the test using EasyMock.

			
package income;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.fail;
import income.exceptions.CalcMethodException;
import income.exceptions.PositionException;
import income.method.ICalcMethod;

import org.easymock.EasyMock;
import org.junit.Before;
import org.junit.Test;

public class IncomeCalculatorTest {

	private ICalcMethod calcMethod;
	private IncomeCalculator calc;

	@Before
	public void setUp() throws Exception {
		calcMethod = EasyMock.createMock(ICalcMethod.class);
		calc = new IncomeCalculator();
	}

	@Test
	public void testCalc1() {
		// Setting up the expected value of the method call calc
		EasyMock.expect(calcMethod.calc(Position.BOSS)).andReturn(70000.0)
				.times(2);
		EasyMock.expect(calcMethod.calc(Position.PROGRAMMER))
				.andReturn(50000.0);
		// Setup is finished need to activate the mock
		EasyMock.replay(calcMethod);

		calc.setCalcMethod(calcMethod);
		try {
			calc.calc();
			fail("Exception did not occur");
		} catch (PositionException e) {

		}
		calc.setPosition(Position.BOSS);
		assertEquals(70000.0, calc.calc());
		assertEquals(70000.0, calc.calc());
		calc.setPosition(Position.PROGRAMMER);
		assertEquals(50000.0, calc.calc());
		calc.setPosition(Position.SURFER);
		EasyMock.verify(calcMethod);
	}

	@Test(expected = CalcMethodException.class)
	public void testNoCalc() {
		calc.setPosition(Position.SURFER);
		calc.calc();
	}

	@Test(expected = PositionException.class)
	public void testNoPosition() {
		EasyMock.expect(calcMethod.calc(Position.BOSS)).andReturn(70000.0);
		EasyMock.replay(calcMethod);
		calc.setCalcMethod(calcMethod);
		calc.calc();
	}

	@Test(expected = PositionException.class)
	public void testCalc2() {
		// Setting up the expected value of the method call calc
		EasyMock.expect(calcMethod.calc(Position.SURFER)).andThrow(
				new PositionException("Don't know this guy")).times(1);

		// Setup is finished need to activate the mock
		EasyMock.replay(calcMethod);
		calc.setPosition(Position.SURFER);
		calc.setCalcMethod(calcMethod);
		calc.calc();
	}

}

		

The expect method tells easy mock to expect a certain method with certain arguments. andReturn defines the return value of this method. The method times defines how often the Mock object will be called.

The reply method needs to be called to make the Mock object available.

After execution of the test you can call the method verify to check if the Mock Object was called as defined.

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