Java Unit Testing Frameworks Compared: JUnit vs TestNG
JUnit and TestNG are the most popular unit testing frameworks for Java code. This post provides an overview of their similarities and differences.
While they are the most well-known frameworks for unit testing Java code, JUnit is actually vastly more popular than TestNG. The stats surprised us: while JUnit is reportedly used by 85% of developers, only about 8% use TestNG!
Both JUnit and TestNG are open-source tools that have some overlapping functionality (with some differences), so which one you’ll end up using will mostly depend on the history of your team and requirements of your project. Let’s see a detailed comparison to help you choose the right unit testing framework for your projects' needs!
JUnit vs TestNG: similarities and differences
Let’s start with some key commonalities between these unit testing frameworks. For one, there are integrations for popular IDEs (IntelliJ IDEA, Eclipse, NetBeans) and they both work with Maven and Gradle. However, one difference is that JUnit supports Visual Studio Code, while with TestNG, you’ll need to rely on a workaround if you are a VS Code user.
Annotations and assertions
JUnit and TestNG both use the well-known system of annotations and assertions, but there’s a slight difference in assertion mechanisms.
Specifically, TestNG offers two ways for assertion: Soft and Hard Assertions, which will define how the test behaves. With Soft Assertions, a thrown exception means that the failing assertion will be logged but the test execution doesn’t stop. With Hard Assertions, the failure of an assertion will fail the whole test run.
The two frameworks use slightly different, but similarly used annotations. In short, TestNG offers additional pairs of annotations for better control over test suites and groups. See the documentation of JUnit and TestNG for more in-depth information, and check out the table below for a quick glance at how annotations are different in JUnit vs TestNG:
Different annotations in JUnit vs TestNG
Used to specify a method as a test method.
The method will be executed once before the current test suite is executed.
The method will be executed once after the current test suite is executed.
The method will be executed once before the first test method in the class is executed.
The method will be executed once after the last test method in the class is executed.
The method will be executed before the test methods declared in
testng.xml (inside the
The method will be executed after the test methods declared in
testng.xml (inside the
The method will be executed before each test method annotated with @Test.
The method will be executed after each test method annotated with @Test.
Used to disable the execution of a specific test (skip test).
Used to time out a test run (e.g. tests that take longer than 1000 milliseconds will fail).
Used to verify that the test throws a specific exception.
The method will be executed before the test methods that belong to a specific group are executed.
The method will be executed after the test methods that belong to a specific group are executed.
Used to specify the order of test execution.
Test creation & execution
TestNG and JUnit both provide the option to use parameterized tests and test suites. However, the way they do it is different: with TestNG,
testng.xml is used to define the parameter names and values, and the annotation
@Parameters used in the test then defines which values to use from
testng.xml. With JUnit, you can use the
@ParameterizedTest annotation to declare a parameterized test, and an additional data source is also defined via the annotation.
Each tool provides the option to use timeouts for tests (learn more in the documentation of TestNG and JUnit 5), enables you to ignore tests (TestNG, JUnit 5), and enables you to define the order you want your tests to be executed in (see the documentation for TestNG and JUnit 5).
Test execution & execution order
JUnit and TestNG offer different ways to manage test execution and execution order. JUnit lets you use assumptions to skip certain tests based on specified conditions (assumptions), but that is not supported by TestNG. For conditional test running in TestNG, you’ll use the SkipException type. On the other hand, for a long while, JUnit has not natively supported parallel test execution, but JUnit version 5.3 changed that with an experimental feature.
Finally, both tools also offer reporting functionality. Again, there are some minor differences: JUnit needs to be integrated with Maven for HTML reports, while with TestNG, that’s just an option as it has HTML reports built in.
Should you use JUnit or TestNG for your project?
As these two frameworks have continued to evolve, the differences between JUnit and TestNG have become less considerable. When trying to decide which one to use, here are a few key considerations:
- In general, we suggest going with the more common JUnit framework because it is more likely to be familiar to your fellow developers.
- If you strongly need parallel test execution and JUnit’s experimental support is no option for you, you’ll need to go with TestNG.
Create unit tests faster
Ultimately, if you’re looking to manage unit tests, both JUnit and TestNG will do the job. But no matter which one you pick, you’ll still have to write those tests manually. That can take a good while – and we haven’t even mentioned maintaining your tests upon code changes. That’s why we created our IDE plugin Symflower which serves as your fast track to robust unit testing.
Use Symflower to generate test templates (boilerplate code) and full unit test suites for plain Java applications, Spring applications and Spring Boot applications. The plugin also provides test-backed code diagnostics (inline suggestions), right as you code. All this fully integrates into your workflow and is available in your IDE! See how it works below, or try Symflower right away: