Java Unit Testing with JUnit

Image Source: https://junit.org/

In this blog post, I have written about unit testing and use of JUnit for Java programming. The first section of this blog post includes the unit testing example without using any IDE and second section includes the unit testing example using IntelliJ IDEA.

JUnit is a unit testing framework for Java programming. JUnit is open source and popular unit testing framework for Java programming.

I am assuming that you have already installed JDK and configured environment variables. Here, we are performing unit testing on interest calculation and formula for interest calculation is given below:

I = PTR / 100

Unit Testing ( No IDE)

1. Download JUnit.jar and Hamcrest-core.jar.
• junit-4.12.jar ( link ) (latest version available at time of the post)
• hamcrest-core-1.3.jar ( link ) (latest version available at time of the post)
  
2. Create a project directory, copy these jars to the newly created directory. All java files and classes are stored inside the directory.
   
3. Create Calculator.java, that includes the main logic of calculating the Interest.

public class Calculator{

 // default values
 double p = 0.0;
 double t = 0.0;
 double r = 0.0;

 // constructor that updates the values
 public Calculator(double p, double t, double r){
  this.p = p;
  this.t = t;
  this.r = r;
 }

 // method that calculates the interest
 public double calculateInterest(){
  return p*t*r / 100;
 }
}

4. Create TestCalculator.java, this is where you compare the results.
import org.junit.Test;
import org.junit.Before;
import static org.junit.Assert.assertEquals;

public class TestCalculator{

 Calculator calculator = null;

 // values for your test case
 double p = 10000.0;
 double t = 1.0;
 double r = 10.0;

 // this run at every test
 @Before
 public void setUp() throws Exception{
  calculator = new Calculator(p, t, r);
 }

 // TEST
 @Test
 public void testCalculateInterest(){
  assertEquals(1000.0, calculator.calculateInterest(), 0.0);
 }
}

5. Create TestRunner.java, this includes the test classes to perform test.

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

public class TestRunner{

 public static void main(String[] str){

  // Run test classes and grab result
  Result result = JUnitCore.runClasses(TestCalculator.class);

  // Test result
  System.out.println(result.wasSuccessful());

  // print the failure message if failure
  for(Failure failure : result.getFailures()){
   // print string 
   System.out.println(failure.toString());
  }

 }
}

6. Compile with JUnit and hamcrest.
   

   javac -classpath junit-4.12.jar;hamcrest-core-1.3.jar;. Calculator.java TestCalculator.java TestRunner.java 
   

7. Now run, reminder : TestRunner includes the main method,
   

   java -classpath junit-4.12.jar;hamcrest-core-1.3.jar;. TestRunner
   

8. And yey, test is successful, now try to change some values.

Continue (Unit Testing using IntelliJ)

References:

• https://github.com/junit-team/junit4/wiki/Getting-started
• https://www.jetbrains.com/help/idea/configuring-testing-libraries.html