Headless execution in Selenium Java - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of Selenium Headless Chrome Setup

What will be the output of the following Java Selenium code snippet when run in headless mode?

Selenium Java

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import org.openqa.selenium.chrome.ChromeOptions;

public class HeadlessTest {
    public static void main(String[] args) {
        ChromeOptions options = new ChromeOptions();
        options.addArguments("--headless");
        WebDriver driver = new ChromeDriver(options);
        driver.get("https://example.com");
        String title = driver.getTitle();
        System.out.println(title);
        driver.quit();
    }
}

A Prints an empty string and exits normally

B Throws a WebDriverException due to missing GUI

C Prints "Example Domain" and exits normally

D Throws a NullPointerException at getTitle()

💡 Hint

Headless mode runs browser without GUI but still loads pages fully.

In headless mode, Chrome loads pages normally but without opening a visible window. The title of https://example.com is "Example Domain", so the code prints that and exits cleanly.

❓ assertion

intermediate

Correct Assertion for Headless Page Title

Which assertion correctly verifies the page title in a Selenium Java test running in headless mode?

Selenium Java

import static org.junit.jupiter.api.Assertions.assertEquals;

// Assume driver is a valid WebDriver instance running headless
String actualTitle = driver.getTitle();

A assertFalse(actualTitle.isEmpty());

B assertEquals(actualTitle, "Example Domain");

C assertTrue(actualTitle.contains("Example"));

D assertEquals("Example Domain", actualTitle);

💡 Hint

Check the order of expected and actual in assertEquals.

The correct order in assertEquals is assertEquals(expected, actual). Option D uses this order and checks exact title match.

🔧 Debug

advanced

Debugging Headless Chrome Timeout

A Selenium test running Chrome in headless mode fails with a timeout error when loading a page. Which is the most likely cause?

A Incorrect ChromeDriver version incompatible with Chrome browser

B Missing --disable-gpu argument causing rendering issues

C Headless mode disables network requests by default

D Page requires user interaction which headless mode cannot perform

💡 Hint

Check compatibility between driver and browser versions.

Timeouts often happen if ChromeDriver version does not match the installed Chrome browser version, causing failures to load pages.

🧠 Conceptual

advanced

Advantages of Headless Browser Testing

Which of the following is NOT an advantage of running Selenium tests in headless mode?

A Ability to run tests on servers without display environments

B Easier debugging by visually seeing browser actions

C Faster test execution due to no GUI rendering

D Reduced resource usage compared to full browser mode

💡 Hint

Think about what headless mode means for visual feedback.

Headless mode does not show a GUI, so you cannot visually see browser actions, making debugging harder, not easier.

❓ framework

expert

Configuring Headless Mode in Selenium Test Framework

In a Java Selenium test framework using JUnit 5, which code snippet correctly configures ChromeDriver to run all tests in headless mode with proper setup and teardown?

A

private WebDriver driver;

@BeforeEach
void setup() {
  ChromeOptions options = new ChromeOptions();
  options.addArguments("--headless");
  driver = new ChromeDriver(options);
}

@AfterEach
void teardown() {
  driver.quit();
}

B

private WebDriver driver;

@BeforeAll
static void setup() {
  ChromeOptions options = new ChromeOptions();
  options.addArguments("--headless");
  driver = new ChromeDriver(options);
}

@AfterAll
static void teardown() {
  driver.quit();
}

C

private static WebDriver driver;

@BeforeEach
void setup() {
  ChromeOptions options = new ChromeOptions();
  options.addArguments("--headless");
  driver = new ChromeDriver(options);
}

@AfterEach
void teardown() {
  driver.quit();
}

D

private static WebDriver driver;

@BeforeAll
static void setup() {
  ChromeOptions options = new ChromeOptions();
  options.addArguments("--headless");
  driver = new ChromeDriver(options);
}

@AfterAll
static void teardown() {
  driver.quit();
}

💡 Hint

Remember JUnit 5 lifecycle annotations and static context rules.

In JUnit 5, @BeforeEach and @AfterEach methods are instance methods (non-static). Driver should be instance variable to avoid sharing state between tests. Option A follows this correctly.

Practice

1. What is the main purpose of running Selenium tests in headless mode?

easy

A. To run tests without opening the browser window

B. To slow down the test execution for debugging

C. To enable visual testing with screenshots

D. To run tests only on mobile devices

Solution

1. Step 1: Understand headless mode concept

   Headless mode means running browser tests without showing the browser window on screen.

2. Step 2: Identify the main purpose

   This mode is mainly used to run tests faster and on servers where no display is available.

3. Final Answer:

   To run tests without opening the browser window -> Option A

4. Quick Check:

   Headless mode = No browser window [OK]

Hint: Headless means no visible browser window during tests [OK]

Common Mistakes:

• Thinking headless slows down tests
• Confusing headless with mobile testing
• Assuming headless always shows screenshots

2. Which of the following is the correct way to enable headless mode for ChromeDriver in Selenium Java?

easy

A. ChromeOptions options = new ChromeOptions(); options.setHeadless(true);

B. ChromeOptions options = new ChromeOptions(); options.addArguments("--headless");

C. ChromeOptions options = new ChromeOptions(); options.addArguments("headless-mode");

D. ChromeOptions options = new ChromeOptions(); options.enableHeadless();

Solution

1. Step 1: Recall correct syntax for headless mode

   In Selenium Java, headless mode is enabled by adding the argument "--headless" to ChromeOptions.

2. Step 2: Check each option

   Only ChromeOptions options = new ChromeOptions(); options.addArguments("--headless"); uses the correct method and argument syntax.

3. Final Answer:

   ChromeOptions options = new ChromeOptions(); options.addArguments("--headless"); -> Option B

4. Quick Check:

   Use addArguments("--headless") to enable headless [OK]

Hint: Use addArguments("--headless") to enable headless mode [OK]

Common Mistakes:

• Using incorrect argument names like "headless-mode"
• Trying to call non-existent methods like enableHeadless()
• Assuming setHeadless(true) exists in ChromeOptions

3. What will be the output when running the following Selenium Java code snippet?

ChromeOptions options = new ChromeOptions();
options.addArguments("--headless");
WebDriver driver = new ChromeDriver(options);
driver.get("https://example.com");
System.out.println(driver.getTitle());
driver.quit();

medium

A. Prints an empty string because page did not load

B. Throws an error because headless mode cannot get page titles

C. Prints the page title of https://example.com without opening a browser window

D. Opens a visible browser window and prints the title

Solution

1. Step 1: Understand headless mode behavior

   Headless mode runs browser without UI but still loads pages and executes scripts normally.

2. Step 2: Analyze code output

   The code loads example.com and prints its title. This works fine in headless mode.

3. Final Answer:

   Prints the page title of https://example.com without opening a browser window -> Option C

4. Quick Check:

   Headless loads page and gets title correctly [OK]

Hint: Headless runs full browser logic but no UI shown [OK]

Common Mistakes:

• Assuming headless mode disables page loading
• Thinking getTitle() returns empty in headless
• Expecting visible browser window in headless mode

4. Identify the error in the following Selenium Java code snippet intended to run Chrome in headless mode:

ChromeOptions options = new ChromeOptions();
options.addArguments("headless");
WebDriver driver = new ChromeDriver(options);
driver.get("https://example.com");

medium

A. The argument should be "--headless" with two dashes

B. ChromeOptions cannot be used with ChromeDriver

C. WebDriver must be cast to ChromeDriver explicitly

D. The get() method cannot be called in headless mode

Solution

1. Step 1: Check argument syntax for headless mode

   The correct argument to enable headless mode is "--headless" with two dashes, not "headless".

2. Step 2: Verify other code parts

   Using ChromeOptions with ChromeDriver and calling get() is valid. No casting needed.

3. Final Answer:

   The argument should be "--headless" with two dashes -> Option A

4. Quick Check:

   Use "--headless" argument exactly [OK]

Hint: Headless argument needs two dashes: "--headless" [OK]

Common Mistakes:

• Using single dash or no dash in headless argument
• Thinking ChromeOptions can't be passed to ChromeDriver
• Believing get() is disabled in headless mode

5. You want to run Selenium tests in headless mode on both Chrome and Firefox browsers using Java. Which approach correctly sets headless mode for both browsers?

hard

A. Use ChromeOptions.setHeadless(true) for Chrome and FirefoxOptions.addArguments("--headless") for Firefox

B. Use ChromeOptions.setHeadless(true) for Chrome and FirefoxOptions.setHeadless(true) for Firefox

C. Use ChromeOptions.addArguments("--headless") for Chrome and FirefoxOptions.addArguments("headless") for Firefox

D. Use ChromeOptions.addArguments("--headless") for Chrome and FirefoxOptions.setHeadless(true) for Firefox

Solution

1. Step 1: Recall how to enable headless mode in Chrome and Firefox

   In Selenium Java, Chrome uses addArguments("--headless") to enable headless mode. FirefoxOptions has a setHeadless(true) method.

2. Step 2: Match correct methods for each browser

   Use ChromeOptions.addArguments("--headless") for Chrome and FirefoxOptions.setHeadless(true) for Firefox correctly uses addArguments for Chrome and setHeadless for Firefox.

3. Final Answer:

   Use ChromeOptions.addArguments("--headless") for Chrome and FirefoxOptions.setHeadless(true) for Firefox -> Option D

4. Quick Check:

   Chrome uses addArguments, Firefox uses setHeadless [OK]

Hint: Chrome uses addArguments, Firefox uses setHeadless(true) [OK]

Common Mistakes:

• Using setHeadless(true) for Chrome which does not exist
• Using incorrect argument like "headless" without dashes for Firefox
• Mixing methods between browsers incorrectly