In this chapter, we'll learn how to integrate JUnit and Mockito together. Also we will see the use of @InjectMocks, @Mock annotation.
Here we will create a Math Application which uses "CalculatorService" to perform basic mathematical operations such as addition, subtraction, multiply, and division.
We'll use Mockito to mock the dummy implementation of "CalculatorService". In addition, we've made extensive use of annotations to showcase their compatibility with both JUnit and Mockito.
The process is discussed below in a step-by-step manner.
Step 1 − Create an interface called CalculatorService to provide mathematical functions
File: CalculatorService.java
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
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 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);
//test the add functionality
Assert.assertEquals(mathApplication.add(10.0, 20.0),30.0,0);
}
}
Step 4 − Create a class to execute to test cases
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 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
To learn more about JUnit, please refer to JUnit Tutorial at JavaHub Point.