Writing Parallel Tests with TestNG in Selenium Java
Testing web applications with Selenium is a common practice among developers and QA engineers, but as your test suite grows, execution time becomes a major concern. Running tests sequentially can slow down feedback loops and delay releases. That’s where parallel testing comes in—and with TestNG, implementing parallel execution in Selenium becomes fast and straightforward.
In this blog post, we’ll explore how to run Selenium WebDriver tests in parallel using TestNG, boosting efficiency without compromising reliability.
Why Parallel Testing?
Parallel testing allows you to execute multiple test cases simultaneously instead of sequentially. This has several advantages:
- Faster Execution: Drastically reduces the time needed to run all tests.
- Efficient Resource Utilization: Makes better use of CPU cores and system memory.
- Scalability: Essential for large test suites or continuous integration pipelines.
Getting Started with TestNG
TestNG is a powerful testing framework for Java, offering advanced features such as annotations, parameterization, grouping, and parallel execution.
To use TestNG, first add the following Maven dependency in your pom.xml:
xml
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<dependency>
<groupId>org.testng</groupId>
<artifactId>testng</artifactId>
<version>7.8.0</version>
<scope>test</scope>
</dependency>
Also include the Selenium WebDriver dependency:
xml
<dependency>
<groupId>org.seleniumhq.selenium</groupId>
<artifactId>selenium-java</artifactId>
<version>4.18.1</version>
</dependency>
Sample Test Class
Let’s create a simple test class that opens a browser and visits a URL:
java
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import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import org.testng.annotations.Test;
public class GoogleSearchTest {
@Test
public void testGoogleSearch() {
WebDriver driver = new ChromeDriver();
driver.get("https://www.google.com");
System.out.println("Title: " + driver.getTitle());
driver.quit();
}
}
Now, let’s say you have multiple similar tests in different classes or methods—you can run them in parallel using TestNG's configuration.
Configuring Parallel Tests in TestNG
To run tests in parallel, create a testng.xml file and define the parallel execution settings:
xml
<suite name="ParallelSuite" parallel="methods" thread-count="3">
<test name="ParallelTests">
<classes>
<class name="tests.GoogleSearchTest" />
<class name="tests.BingSearchTest" />
<class name="tests.DuckDuckGoSearchTest" />
</classes>
</test>
</suite>
parallel="methods": Runs test methods in parallel.
thread-count="3": Defines how many threads (i.e., tests) can run concurrently.
You can also set parallel="classes" to execute entire classes in parallel.
Thread Safety in Selenium
Parallel execution means multiple browser instances are launched simultaneously. To avoid conflicts, always use local instances of WebDriver in each test method. Avoid using static or shared drivers unless you use thread-local patterns.
java
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ThreadLocal<WebDriver> driver = new ThreadLocal<>();
@BeforeMethod
public void setup() {
driver.set(new ChromeDriver());
}
@Test
public void testSearch() {
driver.get().get("https://example.com");
}
@AfterMethod
public void tearDown() {
driver.get().quit();
driver.remove();
}
Conclusion
Parallel testing with TestNG and Selenium is an essential practice for speeding up test execution and achieving faster delivery cycles. With just a few configuration tweaks, you can scale your testing efforts and make full use of your development and CI environments.
Whether you're testing across multiple browsers, validating different modules, or running hundreds of regression tests—TestNG's parallel execution capabilities can save hours of time while maintaining test reliability. Give it a try, and start running your Selenium tests in parallel today.
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