EasyMock - createNiceMock

EasyMock.createNiceMock() creates mock and set the default implementation of each method of the mock. If EasyMock.createMock() is used then mock method invocation will throw assertion error.

Syntax

calcService = EasyMock.createNiceMock(CalculatorService.class);

Example

Create an Interface CalculatorService whose purpose to provide various calculation related functions.

public interface CalculatorService {
   public double add(double input1, double input2);
   public double subtract(double input1, double input2);
   public double multiply(double input1, double input2);
   public double divide(double input1, double input2);
}

Create a JAVA class to represent MathApplication.

public class MathApplication {
   private CalculatorService calcService;

   public void setCalculatorService(CalculatorService calcService){
      this.calcService = calcService;
   }
   public double add(double input1, double input2){
      return calcService.add(input1, input2);		
   }
   public double subtract(double input1, double input2){
      return calcService.subtract(input1, input2);
   }
   public double multiply(double input1, double input2){
      return calcService.multiply(input1, input2);
   }
   public double divide(double input1, double input2){
      return calcService.divide(input1, input2);
   }
}

Let's test the MathApplication class, by injecting in it a mock of calculatorService. Mock will be created by EasyMock.

Here we've added one mock method calls, add() via expect(). But during testing, we've called substract() and other methods as well. When we create mock object using EasyMock.createNiceMock(), default implementation with default values are available.

import org.easymock.EasyMock;
import org.easymock.EasyMockRunner;
import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;

@RunWith(EasyMockRunner.class)
public class MathApplicationTester {
	
   private MathApplication mathApplication;
   
   private CalculatorService calcService;

   @Before
   public void setUp(){
      mathApplication = new MathApplication();
      calcService = EasyMock.createNiceMock(CalculatorService.class);
      mathApplication.setCalculatorService(calcService);
   }

   @Test
      public void testCalcService(){
      //add the behavior to add numbers
      EasyMock.expect(calcService.add(20.0,10.0)).andReturn(30.0);
      //activate the mock
      EasyMock.replay(calcService);	
      //test the add functionality
      Assert.assertEquals(mathApplication.add(20.0, 10.0),30.0,0);
      //test the substract functionality
      Assert.assertEquals(mathApplication.subtract(20.0, 10.0),0.0,0);
      //test the multiply functionality
      Assert.assertEquals(mathApplication.divide(20.0, 10.0),0.0,0);		
      //test the divide functionality
      Assert.assertEquals(mathApplication.multiply(20.0, 10.0),0.0,0);

      //verify call to calcService is made or not
      EasyMock.verify(calcService);
   }
}

Create a java class file name TestRunner in C:\ > EasyMock_WORKSPACE to execute Test case(s)

import org.junit.runner.JUnitCore;
import org.junit.runner.Result;
import org.junit.runner.notification.Failure;

public class TestRunner {
   public static void main(String[] args) {
      Result result = JUnitCore.runClasses(MathApplicationTester.class);
      for (Failure failure : result.getFailures()) {
         System.out.println(failure.toString());
      }
      System.out.println(result.wasSuccessful());
   }
}  	

Verify the Result

Compile the classes using javac compiler as follows

C:\EasyMock_WORKSPACE>javac MathApplicationTester.java

Now run the Test Runner to see the result

C:\EasyMock_WORKSPACE>java TestRunner

Verify the output.

true