JUnit vs. TestNG: Choosing a Framework for Unit Testing

Software testing is not a single activity; it consists of multiple testing scenarios that are covered throughout the development process and can even be categorized in multiple ways. One way to categorize is on the basis of testing levels: unit testing, integration testing, and system testing.

Unit testing is performed during coding. Every small, testable part, known as a unit, of a project is verified and tested to ensure that the application works as expected. In short, we can say that unit testing is the root of effective software development.

There are multiple frameworks available for unit testing, and for any type of programming language. For Java developers, JUnit and TestNG are the most widely used. These frameworks are siblings and have the same test roots, and the debate over which is better is as complex as the browser wars.

Let’s look at how these two testing frameworks are different from each other, and which framework is better suited for your unit testing.

What Is JUnit?

JUnit is one of the most widely used open source testing frameworks based on Java. It is a unit testing framework used for writing and running tests.

Based initially on SUnit and written in Smalltalk, JUnit is used to create Selenium WebDriver tests in Java. It was first introduced in 1997, and since then, it has been considered the standard for testing applications based on Java and many other languages.

The latest version of JUnit, JUnit 5, was redesigned a lot to overcome the limitations of previous JUnit versions.

What Is TestNG?

TestNG is another popular Java-based testing framework and is similar to JUnit. However, TestNG is configured with some advanced functionalities and special annotations that are not supported by Junit—the “NG” stands for “next generation.” TestNG was created in 2004 and is now on version 7.

TestNG was built to be more flexible than JUnit, and it can cover almost every category of software testing, including unit, end-to-end, functional, and integration. TestNG might be inspired from JUnit, but it is neither an extension nor an upgraded version of JUnit.

JUnit vs. TestNG

Let’s see a better comparison of these frameworks and analyze how each is used for unit testing, based on different tests.

Annotations

Both JUnit and TestNG are annotation-based testing frameworks, and most of the annotations in both frameworks are similar. For instance, in JUnit, the @ignore annotation is used to ignore a test, which is similar to the @Test(enable=false) annotation in TestNG. The @Before annotation in JUnit also is similar to the @BeforeMethod annotation in TestNG.

An annotation difference between JUnit 4 and TestNG is that in JUnit 4, you had to declare @BeforeClass and @AfterClass as a static method, whereas in TestNG, there are no such constraints for using the static method. 

A better comparison of annotations for both these frameworks is described in the table below:

Test Suite

Integrating multiple unit tests together and then running them in parallel as a test suite used to be a feature available for only TestNG, but now it is available in JUnit 5 as well. However, the method of implementing it is slightly different.

In JUnit, the test suite is run using the @RunWith and @Suite annotations. Below is a class that describes how two unit tests, “JUnitTest 1” and “JUnitTest 2,” run together after executing JUnitTest 5.

TestNG uses an XML file to run the suite test. The below XML file defines how two unit tests, “TestNGTest1” and “TestNGTest2,” will run together.

TestNG lets you execute tests in many ways with multiple threads, while allowing you to run test classes and methods in parallel. 

Ignore Test

The “Ignore test” feature is used to clarify whether a unit test should be ignored or not. This feature is available with both JUnit 5 and TestNG, with the annotations detailed in the table above.

Exception Test

An exception test verifies what exception should be thrown from the unit test. This feature is also available with both JUnit 5 and TestNG.

For JUnit 5:

For TestNG:

Time Test

A time test is yet another class that is used to define whether a unit test takes longer than the specified number of milliseconds to run; if so, then it will terminate the test and mark it as failed. Both JUnit 5 and TestNG are implemented with this feature.

For JUnit 5:

For TestNG:

Group Test

A group test is a new feature that is only available with TestNG. A group test enables you to forward methods in the right portions, perform complex grouping of test methods, and run multiple tests with the “Groups” annotation, saving you both time and money.

It provides flexibility to divide your tests and eliminate the need for recompiling anything, even if you wish to run different sets of tests back to back. As it is only implemented on TestNG, you don’t get this flexibility with JUnit. However, JUnit 5 has introduced a new concept that is similar to Groups, called Tag.

In TestNG, groups are specified in the XML file with the “groups” tag. You can easily locate it under the <test> or <suite> tag.

Reporting

Reporting is a vital part of testing, as it allows testers to understand the results of an executed test, points of failure, and the reasons for failure. Logging is essential to keep a watch on the execution flow and debug issues if a test fails.

The TestNG framework automatically generates test reports for test executions, which also includes HTML and XML report output. It also enables testers to write their own report and use it with TestNG. Another option that TestNG offers is that it allows users to write their own logs that are notified during runtime by TestNG.

JUnit provides this data in XML format, but it doesn’t create a report for the test execution, which means you’ll have to generate your test report separately.

Parameterized Testing

The primary goal of this testing is to create a collection of as arrays that includes parameters, to define and run multiple test cases. Both JUnit and TestNG are capable of parameterized testing, but they use different approaches.

TestNG supports XML, CSVs, or plain text files for feeding data, in addition to supplying the parameters via coding.

JUnit uses different combinations in multiple arguments to provide a shortcut for a long parameter list; this feature is unavailable with TestNG.

Community Support

When it comes to community support, JUnit has a long and better history with a more extensive user base. Also, as it is the first widely used unit testing framework, it defines the standard for Java unit testing. It’s easier to find the answers for your queries and to talk to other software professionals about JUnit.

On the other hand, TestNG might have a smaller user base, but it doesn’t have little community support. Its website offers support, and there are many community forms that can be used to connect with TestNG users.

Making the Right Choice

Automated testing can be executed with multiple frameworks and tools, depending on the types of testing you’re performing and what your goals are. For automated unit testing, JUnit and TestNG are the most popular and well-supported frameworks available today.

Deciding between JUnit and TestNG can be challenging, as some features that one provides are not available with the other. Also, both frameworks use different annotations and different coding for various tests.

Now that you’ve explored how the two frameworks are different from each other, you can make a more informed choice about which framework you should use for unit testing your web application or website.