Running tests on Grid in Selenium Python - Build an Automation Script

Run a Selenium test on Selenium Grid

Preconditions (3)

Step 1: Open a remote browser session on Selenium Grid using Chrome

Step 2: Navigate to http://example.com/login

Step 3: Enter 'testuser' in the username field with id 'username'

Step 4: Enter 'Password123' in the password field with id 'password'

Step 5: Click the login button with id 'loginBtn'

Step 6: Wait for the page to load and verify the URL contains '/dashboard'

✅ Expected Result: User is successfully logged in and the browser navigates to the dashboard page on the remote Grid node

Automation Requirements - selenium

Assertions Needed:

Verify the current URL contains '/dashboard' after login

Best Practices:

Use Remote WebDriver to connect to Selenium Grid Hub

Use explicit waits to wait for page load or elements

Use By.ID locators for elements

Close the browser session after test

Automated Solution

Selenium Python

from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC


def test_login_on_grid():
    grid_url = "http://localhost:4444/wd/hub"
    capabilities = {
        "browserName": "chrome"
    }

    driver = webdriver.Remote(command_executor=grid_url, desired_capabilities=capabilities)

    try:
        driver.get("http://example.com/login")

        # Enter username
        username_field = WebDriverWait(driver, 10).until(
            EC.presence_of_element_located((By.ID, "username"))
        )
        username_field.send_keys("testuser")

        # Enter password
        password_field = driver.find_element(By.ID, "password")
        password_field.send_keys("Password123")

        # Click login button
        login_button = driver.find_element(By.ID, "loginBtn")
        login_button.click()

        # Wait for URL to contain '/dashboard'
        WebDriverWait(driver, 10).until(
            EC.url_contains("/dashboard")
        )

        # Assertion
        assert "/dashboard" in driver.current_url, "Login failed or dashboard not loaded"

    finally:
        driver.quit()

This test uses Selenium's Remote WebDriver to connect to the Selenium Grid Hub at http://localhost:4444/wd/hub. It specifies Chrome as the browser.

The test navigates to the login page, waits explicitly for the username field to appear, then fills in the username and password fields using By.ID locators.

After clicking the login button, it waits explicitly until the URL contains /dashboard, indicating successful login.

The assertion checks the URL to confirm the dashboard page loaded.

Finally, the browser session is closed with driver.quit() to clean up resources.

Common Mistakes - 4 Pitfalls

Using local WebDriver instead of Remote WebDriver for Grid

Using implicit waits or no waits before interacting with elements

Hardcoding XPath locators instead of using stable locators like ID

Not closing the browser session after test

Bonus Challenge

Now add data-driven testing with 3 different username and password combinations to run the login test multiple times on the Grid.

Show Hint

Practice

1. What is the main purpose of using Selenium Grid when running tests?

easy

A. To run tests on multiple browsers and machines remotely

B. To write test scripts faster

C. To debug tests locally

D. To create test reports automatically

Solution

1. Step 1: Understand Selenium Grid's role

   Selenium Grid allows running tests on different browsers and machines remotely, enabling parallel testing.

2. Step 2: Compare options with Grid's purpose

   Options A, B, and D describe other testing activities but not the main purpose of Selenium Grid.

3. Final Answer:

   To run tests on multiple browsers and machines remotely -> Option A

4. Quick Check:

   Grid purpose = remote multi-browser testing [OK]

Hint: Grid runs tests remotely on many browsers at once [OK]

Common Mistakes:

• Confusing Grid with test script writing tools
• Thinking Grid is for debugging locally
• Assuming Grid creates reports automatically

2. Which of the following is the correct way to create a Remote WebDriver session in Python for Selenium Grid?

easy

A. driver = webdriver.Grid('http://hub:4444')

B. driver = webdriver.Chrome()

C. driver = webdriver.Remote('chrome')

D. driver = webdriver.Remote(command_executor='http://hub:4444/wd/hub', desired_capabilities={'browserName': 'chrome'})

Solution

1. Step 1: Review Remote WebDriver syntax

   Creating a Remote WebDriver requires specifying the Grid Hub URL and desired capabilities as a dictionary.

2. Step 2: Check each option's correctness

   driver = webdriver.Remote(command_executor='http://hub:4444/wd/hub', desired_capabilities={'browserName': 'chrome'}) correctly uses webdriver.Remote with command_executor URL and capabilities. Options A, B, and C are incorrect or invalid syntax.

3. Final Answer:

   driver = webdriver.Remote(command_executor='http://hub:4444/wd/hub', desired_capabilities={'browserName': 'chrome'}) -> Option D

4. Quick Check:

   Remote WebDriver needs hub URL and capabilities [OK]

Hint: Use webdriver.Remote with hub URL and browser capabilities [OK]

Common Mistakes:

• Using webdriver.Chrome() instead of Remote
• Passing browser name directly without capabilities dict
• Using non-existent webdriver.Grid class

3. What will be the output when running this code snippet connected to a Selenium Grid Hub?

from selenium import webdriver
caps = {'browserName': 'firefox'}
driver = webdriver.Remote(command_executor='http://localhost:4444/wd/hub', desired_capabilities=caps)
driver.get('https://example.com')
print(driver.title)
driver.quit()

medium

A. Raises a SyntaxError due to caps dictionary

B. Prints the title of https://example.com and closes the browser

C. Fails to connect because 'firefox' is invalid browserName

D. Prints None and leaves browser open

Solution

1. Step 1: Analyze code behavior with Selenium Grid

   The code creates a Remote WebDriver session for Firefox on the Grid Hub, opens example.com, prints the page title, then quits.

2. Step 2: Validate expected output and errors

   No syntax errors exist. 'firefox' is a valid browserName. The title prints correctly, and driver.quit() closes the session.

3. Final Answer:

   Prints the title of https://example.com and closes the browser -> Option B

4. Quick Check:

   Remote driver opens page, prints title, quits [OK]

Hint: Remote driver prints page title then quits cleanly [OK]

Common Mistakes:

• Thinking caps dictionary causes syntax error
• Assuming 'firefox' is invalid browserName
• Forgetting driver.quit() closes session

4. You wrote this code to run tests on Selenium Grid but get a connection error:

driver = webdriver.Remote(command_executor='http://localhost:5555/wd/hub', desired_capabilities={'browserName': 'chrome'})

What is the most likely cause?

medium

A. The Grid Hub is not running on port 5555

B. The browserName 'chrome' is invalid

C. webdriver.Remote cannot be used with command_executor

D. Missing import statement for webdriver

Solution

1. Step 1: Check connection details in command_executor

   The URL uses port 5555, but Selenium Grid Hub usually runs on port 4444 by default.

2. Step 2: Identify common connection error causes

   If the Hub is not running on port 5555, connection fails. Browser name 'chrome' is valid, webdriver.Remote supports command_executor, and imports are assumed correct.

3. Final Answer:

   The Grid Hub is not running on port 5555 -> Option A

4. Quick Check:

   Wrong Hub port causes connection error [OK]

Hint: Check Hub URL and port carefully for connection errors [OK]

Common Mistakes:

• Assuming browserName 'chrome' is invalid
• Thinking webdriver.Remote disallows command_executor
• Ignoring Hub must be running before connecting

5. You want to run tests on Selenium Grid for Chrome and Firefox browsers simultaneously. Which approach correctly sets this up in Python?

hard

A. Use webdriver.Chrome() and webdriver.Firefox() locally without Remote

B. Set desired_capabilities to {'browserName': 'chrome,firefox'} in one Remote call

C. Create two Remote WebDriver instances with different desired_capabilities and run tests in parallel threads

D. Run tests sequentially on one Remote WebDriver instance switching browsers

Solution

1. Step 1: Understand parallel testing on Selenium Grid

   To test multiple browsers simultaneously, create separate Remote WebDriver instances with specific capabilities for each browser.

2. Step 2: Evaluate options for correctness

   Create two Remote WebDriver instances with different desired_capabilities and run tests in parallel threads correctly describes creating two instances and running them in parallel threads. Use webdriver.Chrome() and webdriver.Firefox() locally without Remote runs locally, not on Grid. Set desired_capabilities to {'browserName': 'chrome,firefox'} in one Remote call incorrectly tries to combine browsers in one call. Run tests sequentially on one Remote WebDriver instance switching browsers runs sequentially, not simultaneously.

3. Final Answer:

   Create two Remote WebDriver instances with different desired_capabilities and run tests in parallel threads -> Option C

4. Quick Check:

   Parallel tests need separate Remote drivers per browser [OK]

Hint: Use separate Remote drivers and threads for parallel browsers [OK]

Common Mistakes:

• Trying to specify multiple browsers in one desired_capabilities dict
• Running tests locally instead of on Grid
• Running tests sequentially instead of parallel