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Java Tutorial for Beginners: A Step-by-Step Guide

Overview

What is Java: A Beginners Guide To Java

Lesson - 1

10 Reasons That Explain Why You Need to Learn Java

Lesson - 2

Java EE Tutorial: All You Need To Know About Java EE

Lesson - 3

How to Implement the Revolutionary OOPs Concepts in Java

Lesson - 4

What Is JDK? Why Do We Need It?

Lesson - 5

One-Stop Solution for Java Installation in Windows

Lesson - 6

Java Programming: The Complete Reference You Need

Lesson - 7

All You Need to Know to Implement JUnit Testing in Java

Lesson - 8

Arrays In Java: Declare, Define, and Access Array

Lesson - 9

10 Best Java Frameworks You Should Know in 2021

Lesson - 10

Top 25 Pattern Programs in Java For Printing Numbers

Lesson - 11

What Are Java Classes and Objects and How Do You Implement Them?

Lesson - 12

What is a Java Lambda Expression and How to Implement It?

Lesson - 13

The Differences Between C++ and Java That You Need To Know

Lesson - 14

What is Exception Handling in Java?

Lesson - 15

How to Get Started With Eclipse IDE?

Lesson - 16

What is Java API and The Need for Java APIs?

Lesson - 17

What Are Java Strings And How to Implement Them?

Lesson - 18

Java vs JavaScript: Know The 8 Major Differences

Lesson - 19

What is Encapsulation in Java and How to Implement It?

Lesson - 20

What is Java Interface and Why it's Needed?

Lesson - 21

Top 10 Brilliant Java Project Ideas You Need to Know

Lesson - 22

Top 60 Java Interview Questions and Answers in 2021

Lesson - 23

Java vs. Python: Which is the Best Programming Language?

Lesson - 24

What is an Abstract Class in Java and How to Implement It?

Lesson - 25

Introduction To Java Servlets and Its Life-Cycle

Lesson - 26

What is Polymorphism in Java and How to Implement It?

Lesson - 27

What Is Junit? a Look Into the Best Java Testing Framework

Lesson - 28

What Is Java JDBC? The Complete Reference

Lesson - 29

What Are Java Collections and How to Implement Them?

Lesson - 30

What is Inheritance in Java and How to Implement It

Lesson - 31
All You Need to Know to Implement JUnit Testing in Java

JUnit makes it possible for Java Developers to handle all levels of Java project development. The framework is one of the most popular frameworks used for both unit testing and UI testing. They focus the entire concept of JUnit on testing first and then coding further, making the approach productive and stable. Here, in the article, we will learn how to perform JUnit Testing in Java.

This article will cover and elaborate on the following topics:

  • What is JUnit? 
  • JUnit Testing in Java

What Is JUnit?

JUnit is an open-source Unit Testing framework for the Java programming language. The term "Unit Testing" refers to the way of testing a unit. 

A unit may be the smallest piece of code that may be fetched from the system. This unit may be a line of the code, a class, or a method. It is better to have as small a code chunk as possible as the tests tend to run faster and provide better insights for small test units.

The JUnit testing framework is widely used by Java developers to write and execute tests. All the test cases have to be re-executed every time a new code is added in order to ensure that nothing is broken. There are graphs in JUnit that represent the progress of the test. When the test runs smoothly, the graph shows green, and when the test fails, it turns red. JUnit Testing makes it possible for developers to develop more reliable and bug-free code.

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Now that the basics of JUnit are clear, let's see how to perform JUnit testing in Java.

JUnit Testing in Java

First, make sure that JUnit is downloaded into your system. Then we will begin with downloading the two Jar files. 

  • Open your browser:
  • In the browser window type “Download JUnit”

https://junit.org/junit4/

  • You will find “About JUnit” as the first option.
  • Go click on that link.
  • There you will find the “Download and Install” option.
  • In that link you will find two jar files:
    • junit.jar
    • Hamcrest.jar
  • Download the two jar files one after the other.

Download_And_Install_JUnit

  • Now open the location where those two jar files are downloaded.
  • Copy the two files.
  • Go to your “Documents”.
  • Then open the “Java Library” folder. 
  • Paste the jar files here.

Then in the same folder make a Java file that contains the code that you wish to execute. 

import org.junit.Test;

import org.junit.Ignore

import org.junit.Assert.assertEquals

public class TestJunit {

   String message = “Simplilearn”;

   @Test

   Public void testPrintMessage() {

      System.out.println(“Inside testPrintMessage()”);

      assertEquals(message, “Simplilearn”);

   }

   Public static void main(String[] argos) {

       TestJunit result = new TestJunit();

       result.testPrintMessage();

   }

}

JUnit_Jar_Files

The next step is to compile this test file. We will be running the Java program in the command prompt.

  • Open the command prompt 

javac -cp junit-4.13.1.jar;. TestJunit.java

java -cp junit-4.13.1.jar;. TestJunit

The javac command is used to convert the .java file to .class file.

Junit_Testing_CMD

The message "Inside testPrintMessage()" on the screen shows that there are no issues with the test case.

Now, to check further, we will make some code changes. We would make the "Simplilearn" in the assertEquals command to be "Simplilearn12".

The new command would be: assertEquals (message, "simplilearn12");

Now, when the commands are again run in the command prompt. We get the output that shows the comparison, which says a "ComparisonFailure".

AsserEquals_Junit

This is how the JUnit testing works, and a comparison shows what should be put in the application to make the test successful.

Conclusion

By now, you would have gained the knowledge of JUnit Testing and understood what is meant by Unit Testing. Moving forth, you saw how JUnit Testing could be done in Java. In that testing, we used the Command Prompt to compare to show what we could do to correct the code. 

To learn more about this topic, you can begin from the basics with our free Java Training. To become a certified Java developer, you can enroll in our Full Stack Java Developer Master's Program or the Java Certification Training Course.  

About the Author

Ishan GabaIshan Gaba

Ishan Gaba is a Research Analyst at Simplilearn. He is proficient in Java Programming, Data Structures, and Project Management. Graduated in Information Technology, Ishan is also passionate about writing and traveling.

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