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Mockito – Varying Calls

Mockito provides the following additional methods to vary the expected call counts.

  • atLeast (int min) − expects min calls.
  • atLeastOnce () − expects at least one call.
  • atMost (int max) − expects max calls.

Example

Step 1 − Create an interface 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.

File: MathApplicationTester.java

import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.when;
import static org.mockito.Mockito.atLeastOnce;
import static org.mockito.Mockito.atLeast;
import static org.mockito.Mockito.atMost;
 
import org.junit.Assert;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.runners.MockitoJUnitRunner;
 
// @RunWith attaches a runner with the test class to initialize the test data
@RunWith(MockitoJUnitRunner.class)
public class MathApplicationTester {
       
   //@InjectMocks annotation is used to create and inject the mock object
   @InjectMocks 
   MathApplication mathApplication = new MathApplication();
 
   //@Mock annotation is used to create the mock object to be injected
   @Mock
   CalculatorService calcService;
 
   @Test
   public void testAdd(){
      //add the behavior of calc service to add two numbers
      when(calcService.add(10.0,20.0)).thenReturn(30.00);
              
      //add the behavior of calc service to subtract two numbers
      when(calcService.subtract(20.0,10.0)).thenReturn(10.00);
      
      //test the add functionality
      Assert.assertEquals(mathApplication.add(10.0, 20.0),30.0,0);
      Assert.assertEquals(mathApplication.add(10.0, 20.0),30.0,0);
      Assert.assertEquals(mathApplication.add(10.0, 20.0),30.0,0);
      
      //test the subtract functionality
      Assert.assertEquals(mathApplication.subtract(20.0, 10.0),10.0,0.0);
      
      //check a minimum 1 call count
      verify(calcService, atLeastOnce()).subtract(20.0, 10.0);
      
      //check if add function is called minimum 2 times
      verify(calcService, atLeast(2)).add(10.0, 20.0);
      
      //check if add function is called maximum 3 times
      verify(calcService, atMost(3)).add(10.0,20.0);     
   }
}

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

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