So far, we’ve used annotations to create mocks. Mockito provides various methods to create mock objects. mock() creates mocks without bothering about the order of method calls that the mock is going to make in due course of its action.
Syntax
calcService = mock(CalculatorService.class);
Example
Step 1 − Create an interface called CalculatorService to provide mathematical functions
File: CalculatorService.java
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
File: MathApplication.java
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 in it a mock of calculatorService. Mock will be created by Mockito.
Here we’ve added two mock method calls, add() and subtract(), to the mock object via when(). However, during testing, we’ve called subtract() before calling add(). When we create a mock object using create(), the order of execution of the method does not matter.
File: MathApplicationTester.java
package com.adglob.mock;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.when;
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
@RunWith(MockitoJUnitRunner.class)
public class MathApplicationTester {
private MathApplication mathApplication;
private CalculatorService calcService;
@Before
public void setUp(){
mathApplication = new MathApplication();
calcService = mock(CalculatorService.class);
mathApplication.setCalculatorService(calcService);
}
@Test
public void testAddAndSubtract(){
//add the behavior to add numbers
when(calcService.add(20.0,10.0)).thenReturn(30.0);
//subtract the behavior to subtract numbers
when(calcService.subtract(20.0,10.0)).thenReturn(10.0);
//test the subtract functionality
Assert.assertEquals(mathApplication.subtract(20.0, 10.0),10.0,0);
//test the add functionality
Assert.assertEquals(mathApplication.add(20.0, 10.0),30.0,0);
//verify call to calcService is made or not
verify(calcService).add(20.0,10.0);
verify(calcService).subtract(20.0,10.0);
}
}
Step 4 − Execute test cases
Create a java class file named TestRunner in C:\> Mockito_WORKSPACE to execute Test case(s).
File: TestRunner.java
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());
}
}
Step 5 − Verify the Result
Compile the classes using the javac compiler as follows −
C:\Mockito_WORKSPACE>javac CalculatorService.java MathApplication.
java MathApplicationTester.java TestRunner.java
Now run the Test Runner to see the result −
C:\Mockito_WORKSPACE>java TestRunner
Verify the output.
true
