Java Toolkit: Testing Tools

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Mateusz Walczak

Dec 30, 2022 • 9 min read
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Test-driven development has become a key focal point in application production. To reduce manual errors and the codebase’s size, the right testing framework must be put in place.

Passing acceptance tests before release is crucial to the entire software development life cycle. A variety of bugs and failed processes litter the first prototypes of every program – and testing the end-to-end-process can be a little tedious, albeit an extremely necessary step.

Automated tests remain a core component of test-driven development, so java developers are always on the lookout for the next great testing framework.

By passing multiple test scenarios on different phases of product development, data-driven testing improves the overall outcome and assures a well-performing product.

In dealing with Java testing tools, it’s important that you understand the scope and use case of the tool you’ll handle.

To that end, one could categorize the Java testing tool as either a unit or component test. We already left some recommendations for code coverage and development tools for Java. In this article, we break down and provide the best Java testing tools.

Choosing a unit testing framework

Unit testing frameworks consist of creating test code that verify the functionality of a small portion of code or part of the application logic. Usually developers create tests for a single method on a small part of functionality, but on rare occasions, a test case for a whole class could be justified.

It's important to remember that unit tests never assess the whole service as this would be considered a component test. For java developers looking to explore different unit testing frameworks, here are the leading tools.

JUnit 5

JUnit 5 is a well established open-source testing framework for Java. As a unit testing tool, JUnit5 is a collection of different modules from different sub-projects.

These subprojects include the JUnit Platform and JUnit Jupiter. Where JUnit Platform serves as a foundation for launching test frameworks on the JVM (Java Virtual Machine), JUnit Juniper contains a data model with a test engine to run Jupiter based tests on the platform.


Spock is another Java testing framework and Groovy applications. It’s inspired by JUnit runner and provides feature methods that describe the properties and aspects that you’d expect to find in the system. The features are then separated into blocks and phases, which makes it very easy to read and understand.


Inspired by JUnit 5, TestNG is an all-in-one testing framework solution providing many services. Besides unit testing, this framework has been designed to cover all sorts of software tests, such as component, integration, and end-to-end tests.

TestNG supports several other features like load testing, dependent test methods, and parallel testing as well. This makes TestNG a good solution if you’d opt to stick with a single framework for all your testing needs.

All of the above have very little difference in the behavior, though semantics and the future possibility of extending the scope should be taken into account by the development team. In any case, selecting the right unit testing framework is a team decision after considering each tool's pros and cons.


Lots of testing frameworks have their own way of assessing the results, like JUnit, but there are also dependencies specifically designed to do that and extend the possibilities of acceptance testing by a huge margin. One of those is AssertJ.

This fluent assertion Java library comes in handy especially in cases where basic methods become repetitive. It provides a set of useful methods that speed up the process of writing tests and make the code readable and conscientious.


Unit tests focus on testing small portions of code, but the code architecture often requires using external or internal resources that might not be wanted to or cannot be executed.

In this situation, mocking frameworks come in handy which allow to set expected results from creating mock objects without ever calling them. Those capabilities are provided by:


The Mockito library enables mock creation, verification and stubbing. With this mocking framework, small portions of logic, as per the unit tests definition can be verified. It allows to fully mock the object or just partially using Spy.


EasyMock is Mockito's main competitor, for which the most notable difference is the lack of support for partial mocking and minute differences in semantics.

If your project calls for partial mocking, Mockito might be a way to go. If there is no need for partial mocking, then it would be up to the team which one to choose. Both serve their purpose.


When writing tests private, final and static methods can sometimes be encountered. Those cannot be tested with just Mockito so it has to be enhanced with PowerMock. At this point, it is worth mentioning that not all testing frameworks cooperate well with PowerMock.

When working with JUnit 5, for example, PowerMock proves incompatible. Instead of PowerMock, it is usually better to rethink the test design or maybe even code portions to make the maintenance easier.

Java testing tools for component testing

Component tests involve testing each object or part of the software separately and are a black box testing type. One tool is especially great to work with in Java and it’s Cucumber.

It is an automated test framework that supports BDD (Behavior Driven Development). Scenarios are created in Gherkin syntax that correspond to logical flow of a component or focuses on parts of its functionalities.

This framework is easy to use and very straightforward. It contains Gherkin feature files with test definitions and Java code files with step definitions. Running them in parallel is also possible. The syntax makes it easier to read by the product team, because it specifies feature behaviors that eventually become tests.

Web tests

There are countless tools for testing web applications – so opting for any one is essentially a matter of preference. Despite the plethora of options, two testing tools for Java are widely known and used.

Selenium WebDriver

Selenium WebDriver is a robust, browser-based testing framework that provides test automation for the web, either locally or remotely – a perfect tool for testing web applications. Selenium WebDriver is in reference to the language bindings, the syntax, and the individual browser controlling code.

As an automation testing framework, it provides a single interface to write test scripts in Java or other languages and is primarily used for automated functional tests. On top of that, Selenium is compatible with programming languages like Java, Python, Ruby, and C#.


Serenity is a Java library that integrates well with Selenium WebDriver and enhances the JUnit capabilities. It can be used to write a wide variety of automated unit tests that verify the functionality of web services. The automation testing framework is designed to serve as living documentation, as well as writing acceptance and regression tests.

Performance tests

Performance testing is a huge topic that covers stress, spike, endurance, load, volume and scalability testing for mobile, frontend and backend applications. Some great performance testing tools and in-depth analysis we mentioned in our blog, among them is one step forward for Java: Gatling.

It’s an open source tool with a paid enterprise version used especially for performance testing. Gatling comes with excellent support of the HTTP protocol.
The load testing tool allows one to record the actions and represent them as Java code.

The tool will run your tests on many load injector machines, aggregate your results live, and close tests once finished.

Java testing frameworks: key takeaways

Test-driven development is a method of implementing software programming that integrates programming, testing, and refactoring in a 3-step process.

Our experience in dealing with test-driven development allows for faster innovation and reduces erroneous source code. As we iteratively combine building and testing to evolve the final product and efficiently meet all requirements.

Here is a short overview of all the tools we mentioned above:

  • For unit testing, JUnit5 is a great option given its community support and large documentation base. If you combine this with AssertJ, Mockito, and Cucumber, you’ll have a complete wheelhouse of tools necessary for most test cases.
    • If you’re looking for just one Java testing framework, consider TestNG.
  • For component tests, Selenium WebDriver and Gatling are your best Java testing frameworks for testing web apps and performance, respectively.

Of course, the actual tools you’ll employ will depend on your development team and their current skills. If you’re not sure which tools to use or how to properly implement correct java testing frameworks to maximize time and budget, Netguru provides consultation services for you and your team.

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Mateusz Walczak

Senior Java Developer at Netguru
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