JUnit vs TestNG: Key Differences

Introduction

JUnit and TestNG are two of the most popular testing frameworks for Java applications. While they share similarities, they also have key differences that impact their usage in different testing scenarios.

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Comparison Table

Feature	JUnit	TestNG
Origin	Developed from xUnit family	Inspired by JUnit but enhanced
Annotations	Uses @Test, @BeforeEach, @AfterEach	Uses @Test, @BeforeMethod, @AfterMethod
Parallel Execution	Not supported in JUnit 4; JUnit 5 has limited support	Fully supported via XML configurations
Data-driven Testing	Uses @ParameterizedTest	Supports @DataProvider for advanced scenarios
Dependency Management	Not natively supported	Supports dependsOnMethods for test dependencies
Suite Execution	Requires external tools like Maven/Gradle	Supports testng.xml for suite execution
Listeners and Reporting	Limited built-in support	Rich listener and reporting mechanisms
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Key Differences Explained

1. Annotations

JUnit and TestNG have similar annotations but differ in naming conventions:

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• JUnit 5: @BeforeEach, @AfterEach, @BeforeAll, @AfterAll
• TestNG: @BeforeMethod, @AfterMethod, @BeforeClass, @AfterClass

2. Parallel Execution

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JUnit does not support parallel test execution natively in JUnit 4. JUnit 5 provides limited parallel execution via a custom execution model. TestNG, on the other hand, offers built-in parallel execution using XML configurations.

3. Data-driven Testing

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TestNG provides a powerful @DataProvider feature, allowing multiple sets of test data to be passed dynamically. JUnit 5 supports parameterized tests but lacks TestNG’s flexibility.

4. Test Dependencies

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JUnit does not support method dependencies. TestNG allows method dependencies via dependsOnMethods, making it useful for integration testing.

Commonly Used TestNG Listeners

TestNG provides several built-in listeners to extend test execution behavior. The most commonly used listeners include:

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1. ITestListener

This listener allows tracking test execution events such as test start, success, failure, and skip.

Key Methods:

• onTestStart(ITestResult result)
• onTestSuccess(ITestResult result)
• onTestFailure(ITestResult result)
• onTestSkipped(ITestResult result)

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2. ISuiteListener

This listener helps in executing actions before and after a test suite runs.

Key Methods:

• onStart(ISuite suite) – Called before the test suite starts.
• onFinish(ISuite suite) – Called after the test suite ends.

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3. IInvokedMethodListener

Used for tracking method-level test execution events.

Key Methods:

• beforeInvocation(IInvokedMethod method, ITestResult testResult)
• afterInvocation(IInvokedMethod method, ITestResult testResult)

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4. IReporter

Used for generating custom reports after test execution.

Key Methods:

• generateReport(List<XmlSuite> xmlSuites, List<ISuite> suites, String outputDirectory)

When to Use Which?

• Use JUnit if you prefer a lightweight, standard framework with better integration into modern Java projects.
• Use TestNG if you need parallel execution, flexible dependencies, and better data-driven testing support.

Conclusion

Both JUnit and TestNG have their strengths and weaknesses. The choice depends on your project needs and testing strategy.

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✅ For enterprise projects requiring advanced test management, TestNG is often the better choice.