TestNG

TestNG is a testing framework setup inspired by JUnit and NUnit but introducing some new functionalities that make it more powerful and easier to use, such as parallel testing and data-driven testing.

When to Use

• Complex Suites: You need granular control over which groups of tests run via XML configuration (testing.xml).
• Parallel Execution: Historically better support for multi-threaded test execution than JUnit.
• Dependencies: Tests that depend on other tests (@Test(dependsOnMethods = { "serverStarted" })).

Quick Start

import org.testng.Assert;
import org.testng.annotations.Test;

public class TestNGExample {
    @Test(groups = { "fast" })
    public void testAdd() {
        Assert.assertEquals(1 + 1, 2);
    }
}

<!-- testng.xml -->
<!DOCTYPE suite SYSTEM "https://testng.org/testng-1.0.dtd" >
<suite name="Suite1" parallel="methods" thread-count="5">
  <test name="test1">
    <classes>
       <class name="com.example.TestNGExample"/>
    </classes>
  </test>
</suite>

Core Concepts

Groups

Tagging tests (@Test(groups = "smoke")). Allows running specific subsets (Include/Exclude in XML).

Data Providers

Native support for passing complex objects to tests.

@DataProvider(name = "test1")
public Object[][] createData1() {
 return new Object[][] {
   { "Cedric", new Integer(36) },
   { "Anne", new Integer(37) },
 };
}

@Test(dataProvider = "test1")
public void verifyData1(String n1, Integer n2) { ... }

Best Practices (2025)

Do:

• Use Soft Assertions: SoftAssert allows the test to continue even if one check fails, reporting all errors at the end.
• Parallelize: Leverage thread-count in CI to speed up execution.

Don’t:

• Don’t use dependsOnMethods for Unit Tests: Unit tests should be independent. Use dependencies only for Integration flows.

References

• TestNG Documentation