Headless testing has become a significant trend in modern web automation, offering numerous advantages for developers and testers. In Selenium, running tests in headless mode allows browsers to operate without the graphical user interface (GUI). This article delves into the concept of headless browser testing, its importance, how to run browsers in headless mode in Selenium with Java, and the benefits and limitations of headless testing.

What is Headless Browser Testing?

Headless browser testing is a method of performing automated tests in web browsers and it doesn’t require the GUI. Headless browsers do not display the complete browser window, instead, it is used to load pages and execute JavaScript. It is particularly valuable if the special integration (CI) or an automated testing environment does not require a GUI

Why is Headless Execution Important?

• Speed: Headless browsers generally perform better in comparison to GUI browsers because the latter do not focus on graphics rendering. This leads to faster tests run through.
• Resource Efficiency: Many tests can be run from the command line, and devoid of a GUI, the environment puts a smaller demand on the station’s hardware.
• CI/CD Integration: A majority of CI/CD pipelines deploy GUI for automation and some require a non-GUI response, particularly for tests. These remain fluid as headless testing accommodates itself into these processes easily.
• Stability: Headless tests for example have been known to help minimize the problem of flaky tests related to GUI interactions due to timing problems.

Running Headless Mode in Selenium for Chrome

Selenium provides the option to run the Chrome browser in headless mode with minimal configuration. To enable headless mode in Chrome, we use the ChromeOptions class and set the --headless flag.

Step-by-Step Implementation:

1. Set up ChromeDriver: Ensure that you have the correct version of ChromeDriver installed for your version of Chrome. You can download it from the official website.
2. Create the WebDriver instance in headless mode:

package browser_specific.headless;

import static org.testng.Assert.assertTrue;

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import org.openqa.selenium.chrome.ChromeOptions;
import org.testng.annotations.AfterClass;
import org.testng.annotations.BeforeClass;
import org.testng.annotations.Test;

import actions.BaseTest;

public class HeadlessChromeTest extends BaseTest {

    private WebDriver driver;

    @BeforeClass
    public void setUp() {
        // Configure ChromeOptions for headless mode
        ChromeOptions options = new ChromeOptions();
        options.addArguments("--headless=new"); // Use new headless mode
        options.addArguments("--disable-gpu"); // Recommended for headless execution
        options.addArguments("--window-size=1920,1080"); // Set specific window size
        driver = new ChromeDriver(options);
    }

    @Test
    public void testHeadless() {
        // Navigate to the webpage
        driver.get("https://bonigarcia.dev/selenium-webdriver-java/web-form.html");

        // Assert that the title contains "Selenium WebDriver"
        assertTrue(driver.getTitle().contains("Selenium WebDriver"), "Title does not match the expected value");
    }

    @AfterClass
    public void tearDown() {
        // Close the browser
        if (driver != null) {
            driver.quit();
        }
    }
}

Output:

Explanation:

• The ChromeOptions object is used to set configurations for the Chrome browser.
• The --headless argument is passed to run Chrome in headless mode.
• The --disable-gpu argument is used to avoid potential issues related to graphics rendering in headless mode.
• Selenium then interacts with the page, even though Chrome is running without a visual interface.

Running Headless Mode in Selenium for Firefox

Similar to Chrome, Firefox can also be run in headless mode using the FirefoxOptions class. Here's how you can set up Firefox for headless testing:

Step-by-Step Implementation:

package browser_specific.headless;

import static org.testng.Assert.assertTrue;

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.firefox.FirefoxDriver;
import org.openqa.selenium.firefox.FirefoxOptions;
import org.testng.annotations.AfterClass;
import org.testng.annotations.BeforeClass;
import org.testng.annotations.Test;

import actions.BaseTest;

public class HeadlessFirefoxTest extends BaseTest {

    private WebDriver driver;

    @BeforeClass
    public void setUp() {
        // Configure FirefoxOptions for headless mode
        FirefoxOptions options = new FirefoxOptions();
        options.addArguments("--headless"); // Enable headless mode
        options.addArguments("--disable-gpu"); // Recommended for headless execution
        options.addArguments("--window-size=1920,1080"); // Set specific window size
        driver = new FirefoxDriver(options);
    }

    @Test
    public void testHeadlessFirefox() {
        // Navigate to the webpage
        driver.get("https://bonigarcia.dev/selenium-webdriver-java/web-form.html");

        // Assert that the title contains "Selenium WebDriver"
        assertTrue(driver.getTitle().contains("Selenium WebDriver"), "Title does not match the expected value");
    }

    @AfterClass
    public void tearDown() {
        // Close the browser
        if (driver != null) {
            driver.quit();
        }
    }
}

Output:

Explanation:

• The FirefoxOptions object is used to configure Firefox's settings.
• The setHeadless(true) method is used to enable headless mode.
• Like the Chrome example, no GUI will be launched, but the WebDriver will interact with the webpage and run the necessary tasks.

Running Headless Mode in Selenium for Edge

Microsoft's Edge browser also supports headless mode, though the process is slightly different due to the Edge WebDriver. Here's how you can run tests in headless mode with Edge:

Step-by-Step Implementation:

package browser_specific.headless;

import static org.testng.Assert.assertTrue;

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.edge.EdgeDriver;
import org.openqa.selenium.edge.EdgeOptions;
import org.testng.annotations.AfterClass;
import org.testng.annotations.BeforeClass;
import org.testng.annotations.Test;

import actions.BaseTest;

public class HeadlessEdgeTest extends BaseTest {

    private WebDriver driver;

    @BeforeClass
    public void setUp() {
        // Configure EdgeOptions for headless mode
        EdgeOptions options = new EdgeOptions();
        options.addArguments("--headless=new"); // Use new headless mode
        options.addArguments("--disable-gpu"); // Recommended for headless execution
        options.addArguments("--window-size=1920,1080"); // Set specific window size
        driver = new EdgeDriver(options);
    }

    @Test
    public void testHeadlessEdge() {
        // Navigate to the webpage
        driver.get("https://bonigarcia.dev/selenium-webdriver-java/web-form.html");

        // Assert that the title contains "Selenium WebDriver"
        assertTrue(driver.getTitle().contains("Selenium WebDriver"), "Title does not match the expected value");
    }

    @AfterClass
    public void tearDown() {
        // Close the browser
        if (driver != null) {
            driver.quit();
        }
    }
}

Output:

This code will open the browser in headless mode and perform the testing.

Benefits of Selenium Headless Testing

• Faster Execution: Which was discussed earlier, headless tests are faster in comparison to regular tests.
• Lower Resource Consumption: Headless tests consume less computational power and, therefore, are suitable for systems with lower performance.
• Suitable for Continuous Integration: Can easily be integrated to CI/CD systems.
• Simplifies Testing Environments: Simplifies test scenarios in a setting where GUIs are a nuisance to the testing process.

Limitations of Selenium Headless Testing

• Limited Debugging: Debugging becomes a process a bit more cumbersome again because of the absence of a graphical interface.
• Potential Differences in Behavior: It also means that in headless mode web applications may have different behavior to full browsers, meaning that if tests are run in this mode, the results can be different from those obtained when tests are run in a full browser.
• Limited Support for Certain Features: A few sophisticated operations may also fail to work properly such as – rendering CSS or JavaScript based web pages.

Conclusion

Automated testing of web applications with Selenium and headless browser is a useful approach to the optimization of a CI/CD process. As useful as it is, it is also important that developers understand its shortcomings. Thus, headless testing is one of the best tools for enhancing the tempo of web application testing.