Mockito - Resetting Mock

Mockito provides the capability to a reset a mock so that it can be reused later. Take a look at the following code snippet.

//reset mock


Here we've reset mock object. MathApplication makes use of calcService and after reset the mock, using mocked method will fail the test.


Step 1 − Create an interface called CalculatorService to provide mathematical 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);

Step 2 − 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);

Step 3 − Test the MathApplication class

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


import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.when;
import static org.mockito.Mockito.reset;
import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.runners.MockitoJUnitRunner;

// @RunWith attaches a runner with the test class to initialize the test data
public class MathApplicationTester {

   private MathApplication mathApplication;
   private CalculatorService calcService;

   public void setUp(){
      mathApplication = new MathApplication();
      calcService = mock(CalculatorService.class);

   public void testAddAndSubtract(){

      //add the behavior to add numbers
      //test the add functionality
      Assert.assertEquals(mathApplication.add(20.0, 10.0),30.0,0);

      //reset the mock   

      //test the add functionality after resetting the mock
      Assert.assertEquals(mathApplication.add(20.0, 10.0),30.0,0);   

Step 4 − Execute test cases

Create a java class file named TestRunner in C:\> Mockito_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()) {

Step 5 − Verify the Result

Compile the classes using javac compiler as follows −

C:\Mockito_WORKSPACE>javac MathApplication.


Now run the Test Runner to see the result −

C:\Mockito_WORKSPACE>java TestRunner

Verify the output.

testAddAndSubtract(MathApplicationTester): expected:<0.0> but was:<30.0>