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Test Driven Development for Java using JUnit | Quick Guide

Navdeep Singh Gill | 16 February 2024

Test Driven Development for Java using JUnit

Introduction To Test Driven Development for Java using JUnit

Before we get started, let us understand some basics. Software testing plays an essential role in the life cycle of software development. Identifying bugs and errors during software development and increasing product quality is imperative. Additionally, we need software testing to ensure that the software fulfils the client specifications, responds correctly to inputs (input validation), runs in a reasonable time (performance testing), is easy to install and run (deployment testing), and meets the stakeholders' goals.

Therefore, one must focus on software testing. There are many approaches, and the TDD approach is one of them. It is a crucial practice for extreme programming, suggesting that the code is developed or changed exclusively based on the Unit Testing.

What is Test Driven Development?

TDD is a software development process which includes test-first development. It means the developer first writes a fully automated test case before writing the production code to fulfil that test and refactoring. Steps for the same are given below.

Step 1: Add a test.

Step 2: Run all the tests and see if any new test fails.

Step 3: Update the code to make it pass the test.

Step 4: Rerun the test; if they fail, then refactor and repeat.

Why is Test Driven Development Important?

1. Requirements - Drive out requirement issues early (more in-depth focus on requirements).

2. Rapid Feedback - Many small changes vs. one significant change.

3. Values Refactoring - Refactor often to lower impact and risk.

4. Design to Test - Testing driving good design practice.

5. Tests as information - Documenting decisions and assumptions.

Unit Testing in Java

In the Java community, it plays a vital role in designing and implementing a software/program.

Test-Driven Development helps the programmer in several ways, such as -

  • Improving the code
  • Side by side, increasing the programmer's productivity.
  • Using the Test-Driven Development concept in our programming skills
  • It will save our time, which is getting wasted on rework.
  • Able to identify the error/problem quicker and faster.
  • The programmer will be able to write small classes focused only on a single functionality instead of the big classes.

What are the best test-driven Development Tools for java?

As discussed above, there are many tools available for testing and improving the overall design and implementation of the software system. Some of the most common testing tools are listed below

1. JUnit for Unit Tests

JUnit is a crucial tool in the Java ecosystem for implementing Test Driven Development (TDD) practices. It provides a robust framework for writing and executing unit tests, allowing developers to verify the correctness of their code at a granular level.

JUnit simplifies the process of writing tests by providing annotations and assertions that make it easy to define test cases and expected outcomes. With JUnit, developers can automate the testing process, ensuring that their code behaves as expected under various conditions.

One of the key benefits of using JUnit is its integration with build tools like Maven and Gradle, making it seamless to incorporate tests into the development workflow. By running JUnit tests regularly, developers can catch bugs early in the development cycle, reducing the cost and effort required to fix them later.

In summary, JUnit is an essential tool for Java developers practicing Test Driven Development. Its simplicity, integration with build tools, and promotion of testing best practices make it an asset for ensuring the quality and correctness of Java codebases.

2. TestNG for Unit Testing

TestNG, inspired by JUnit, offers annotations, parameterized tests, and dependency management for effective unit testing in Java. Its features include parallel execution, data-driven testing, and reporting, making it a powerful tool for writing and executing unit tests.

introduction-icon  How to set up the environment for Test Driven Development in Java

The steps to set up the environment for TDD in Java are listed below

1. Setting up it with JUnit

  • Install Java first.
  • Then we need Eclipse or any other IDE (Integrated Development Environment).
  • Create a new project (Maven project) and place the JUnit maven dependency in the pom.xml file. OR, if it's not a Maven project, then download the JUnit jar and include it in your project.

2. Setting up TestNG for TDD

  • Install Java
  • Then we need Eclipse or any other IDE (Integrated Development Environment).
  • Create a Project: If using Maven, then create a new Maven project. Add TestNG dependency in the `pom.xml` file. OR if not using Maven, then Create a new project in your IDE, then download the TestNG jar and include it in your project.

How to implement Java Test Driven Development using JUnit?

The steps to implement Java TDD are described below

1. Naming Convention for the Test Class

We use common conventions in naming the test class. Let's start with the name of the class which is being tested and assume the name of that class is "Student". In that case, the name of the test class should be "StudentTest". We must append "Test" to it. The same naming convention is used in the case of methods. If there is a method "DisplayStudentAddress()", then the name of the method in testing should be "testDisplayStudentAddress()".

Naming in Production 

Naming in testing

Student  StudentTest
DisplayStudentAddress testDisplayStudentAddress()

2. Separate Packages for Production and Testing Code

It is recommended to use different source directories for production code and testing code. The production code should be placed in "src/main/java", and the testing code should be placed in "src/test/java".

  • Structure and Annotation - The "@Test" annotation (JUnit4/5) indicates that a method should be executed as a test method. It is essential to follow the Arrange Act Assert (AAA) pattern in the test code.
  • Arrange - Create the object or set up the necessary dependencies for the code that will be tested.
  • Act - Execute the method or code that needs to be tested.
  • Assert - Verify if the test result is as expected by using assertions. If the result does not match the expected value, the test will be marked as failed.

3. Unit Testing Implementation

Production Code

public class Student {

public String displayStudentName(String firstName, String lastName) {

return firstName + lastName;



Testing Code

Import org.junit.Test;

Import static org.junit.Assert.*;

Public class StudentTest {


Public void testDisplayStudentName() {

Student student = new Student();

String studentName = student.displayStudentName(“Anshuman”, ”Nain”);

assertEquals(“AnshumanNain”, studentName);



How Can XenonStack Help You?

We follow the Test-Driven Development Approach in developing Enterprise-level Applications following Agile Scrum Methodology.

1. Application Modernization

Re-platforming, re-hosting, recoding, rearchitecting, re-engineering, and interoperability of the Software application for current business needs is called Application Modernization. Its services enable the migration of monolithic applications to new Microservices architecture with Native Cloud Support, including the integration of new functionality to create new value from the existing application.

2. Java Cloud Services

Developed, Deployed, and Managed Agile Java Applications on leading Cloud Service Providers - Google Cloud, Microsoft Azure, AWS, and Container Environments - Docker and Kubernetes.

3. Continuous Integration and Continuous Deployment

Enable Secure Continuous Integration and Continuous Delivery Pipeline with Jenkins/ Bamboo/ TeamCity for delivery, automation, self-service environment, and On-demand. Deploy Java Applications to production by decreasing the time by automating the entire delivery pipeline, comprising build, deploy, test, and release.

4. Microservices Architecture

Take a cloud-native approach to building Enterprise Applications for Web and Mobile with a Microservices Architecture. An application based on Microservices Architecture is Small, messaging–enabled, bounded by contexts, autonomously developed, independently deployable, Decentralized, Language–agnostic, Built and released with automated processes.


In the end, Test Driven Development must be adopted by as many developers as possible to increase their productivity and improve the code quality and the productivity and overall development of software/programs. TDD also leads to more modularized, flexible and extensible code. Discover more about Test Driven Development and TDD Testing.

Read More about Test Driven Development in Python and BDD Testing