Junit Tutorial

This is one of the post  in series of simple Junit tutorials. I loved the book Junit in Action so lots of content is inspired by that book.

I will be explaining with simple example and also from time to time pointing you to read certain pages from API of Junit , so that you can have solid foundation of junit.

Junit is used for unit testing of code we write. When we say unit testing we mean testing as simple as one simple method to see if its is playing as per our expectations.

I will write one simple Calculator Class which has one simple method to add two numbers. We will write junit test to see if our method is implemented in correct way or not.Although this can seem to you , its foolish to test the addition of two numbers , but motive here is to understand the working of junit.

Before going through the tutorials you would like to setup your development environment for the tutorials. Read the previous post on setting up junit while using Ant task

package com.learnjunit;
public class Calculator {

	public double add(double number1, double number2) {
		return number1 + number2;
	}
}

We have one simple Calculator class and one method add which is taking two numbers and returning their sum

Now we would write test case for this class

Best Practice : Name the test class as class with same name as class being tested + word Test so the test class in our case would CalculatorTest.java

package com.learnjunit.test;

import com.learnjunit.*;
import org.junit.Test;
import static org.junit.Assert.*;

public class CalculatorTest {

	/**
	 * Test annotation tells that this method can be tested by junit It can also
	 * accept two things
	 * 
	 * @Test(expected=IndexOutOfBoundsException.class)
	 * @Test(timeout=100)
	 */

	@Test
	public void testadd() {
		Calculator c = new Calculator();
		//Asserts that two doubles or floats are equal to within a positive delta.
		double result=c.add(10,20);
		// Check if result is equal to expected value of 30	
		// IF they are not equal , exception is throws with given message
		assertEquals("Checking add method failed",30,result, 0);

	}
}

 

The line by line explanation for the CalculatorTest.java is as follows

Line 1

We created this class in separate package com.learnjuit.test , its always good practice to keep test code separate from code being tested

Line 3

We are importing the package of class which is being tested ( in this case Calculator.java )

Line 17

We created one method named testadd() which is having annotation @Test , this annotation tells that this method has to be taken up by junit

We created one Calculator object then calculated result based on implementation of add method in Calculator.java

We used assertEquals method to verify if the result is same as the expected one.

 

Things to read from Junit API

Test

Assert ( See various assert Methods)

If you have read the previous tutorial on setting up Ant Junit task then you can run it from command prompt

Go to folder where the build.xml file is

ant junit

The complete test report would be published in the target/test-report folder

You can download the complete source code from this link