Grid setup and configuration in Selenium Python - Test Execution Trace

Test Overview

This test verifies that a Selenium Grid is correctly set up and configured by running a simple test on a remote node. It checks if the browser opens remotely, navigates to a page, and verifies the page title.

Test Code - unittest

Selenium Python

from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.remote.webdriver import WebDriver
import unittest

class TestGridSetup(unittest.TestCase):
    def setUp(self):
        grid_url = "http://localhost:4444/wd/hub"
        capabilities = {
            "browserName": "chrome",
            "platformName": "ANY"
        }
        self.driver: WebDriver = webdriver.Remote(command_executor=grid_url, desired_capabilities=capabilities)

    def test_open_google(self):
        self.driver.get("https://www.google.com")
        title = self.driver.title
        self.assertEqual(title, "Google")

    def tearDown(self):
        self.driver.quit()

if __name__ == '__main__':
    unittest.main()

Execution Trace - 5 Steps

Step	Action	System State	Assertion	Result
1	Test starts and unittest framework initializes	Test runner ready to execute test methods	—	PASS
2	SetUp method creates Remote WebDriver connecting to Selenium Grid at http://localhost:4444/wd/hub with Chrome capabilities	Remote WebDriver session established on Grid node with Chrome browser	Remote WebDriver session is active	PASS
3	Driver navigates to https://www.google.com	Browser on remote node opens Google homepage	Page loaded with title 'Google'	PASS
4	Assertion checks if page title equals 'Google'	Page title retrieved from remote browser	title == 'Google'	PASS
5	tearDown method quits the remote WebDriver session	Remote browser closed and session ended	—	PASS

Failure Scenario

Failing Condition: Selenium Grid hub is not running or node is not registered, causing Remote WebDriver session creation to fail

Execution Trace Quiz - 3 Questions

What does the test verify about the Selenium Grid setup?

A It verifies that the local Chrome browser is installed.

B It verifies that a remote browser session can be created and used to open a webpage.

C It verifies that the Selenium Grid hub is running on port 5555.

D It verifies that the test code runs without any imports.

Key Result

Always verify that the Selenium Grid hub and nodes are running and accessible before running tests that use Remote WebDriver sessions.

Practice

1. What is the main purpose of Selenium Grid in test automation?

easy

A. To generate test reports automatically

B. To run tests on multiple browsers and machines simultaneously

C. To debug test scripts locally

D. To write test scripts faster

Solution

1. Step 1: Understand Selenium Grid's role

   Selenium Grid allows running tests on different browsers and machines at the same time to save time and increase coverage.

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

   Only To run tests on multiple browsers and machines simultaneously describes running tests on multiple browsers and machines simultaneously, which is the core feature of Selenium Grid.

3. Final Answer:

   To run tests on multiple browsers and machines simultaneously -> Option B

4. Quick Check:

   Selenium Grid = Run tests on many browsers/machines [OK]

Hint: Remember Grid = multiple browsers + machines running tests [OK]

Common Mistakes:

• Confusing Grid with test script writing tools
• Thinking Grid generates reports
• Assuming Grid is for debugging only

2. Which Python code snippet correctly creates a Remote WebDriver to connect to a Selenium Grid hub at 'http://localhost:4444/wd/hub' for Chrome browser?

easy

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

B. driver = webdriver.Chrome('http://localhost:4444/wd/hub')

C. driver = webdriver.Remote('chrome', 'http://localhost:4444/wd/hub')

D. driver = webdriver.Remote('http://localhost:4444/wd/hub', browser='chrome')

Solution

1. Step 1: Check Remote WebDriver syntax

   webdriver.Remote requires 'command_executor' URL and 'desired_capabilities' dictionary specifying browser.

2. Step 2: Validate each option

   driver = webdriver.Remote(command_executor='http://localhost:4444/wd/hub', desired_capabilities={'browserName': 'chrome'}) correctly uses command_executor and desired_capabilities with browserName 'chrome'. Others misuse parameters or classes.

3. Final Answer:

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

4. Quick Check:

   Remote WebDriver needs command_executor + desired_capabilities [OK]

Hint: Use command_executor and desired_capabilities keys for Remote [OK]

Common Mistakes:

• Using webdriver.Chrome instead of webdriver.Remote
• Passing URL as first argument without keyword
• Incorrect parameter names like 'browser' instead of 'desired_capabilities'

3. Given this Python code connecting to Selenium Grid:

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)

What will be printed if the Grid and node are correctly set up?

medium

A. Empty string

B. An error about missing local browser

C. The title of the page at https://example.com

D. SyntaxError

Solution

1. Step 1: Understand code execution with Grid

   The code uses Remote WebDriver to open Firefox on Grid node and navigates to example.com.

2. Step 2: Predict output of print(driver.title)

   If Grid and node are correct, driver.title returns the page title of example.com, which is a string like 'Example Domain'.

3. Final Answer:

   The title of the page at https://example.com -> Option C

4. Quick Check:

   Remote driver prints page title when setup is correct [OK]

Hint: Correct Grid setup means driver.title shows page title [OK]

Common Mistakes:

• Expecting local browser errors when Grid is correct
• Thinking driver.title returns empty string by default
• Confusing syntax errors with runtime behavior

4. You wrote this code to connect to Selenium Grid but get a connection error:

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

What is the likely cause and how to fix it?

medium

A. Missing keyword arguments; use command_executor and desired_capabilities keywords

B. Wrong URL; should be 'http://localhost:5555/wd/hub'

C. Browser name must be uppercase 'Chrome'

D. webdriver.Remote does not support Chrome browser

Solution

1. Step 1: Identify correct webdriver.Remote syntax

   webdriver.Remote requires keyword arguments: command_executor for URL and desired_capabilities for browser info.

2. Step 2: Analyze given code

   Code passes URL and capabilities as positional arguments without keywords, causing connection error.

3. Final Answer:

   Missing keyword arguments; use command_executor and desired_capabilities keywords -> Option A

4. Quick Check:

   webdriver.Remote needs command_executor and desired_capabilities keywords [OK]

Hint: Always use command_executor and desired_capabilities keywords [OK]

Common Mistakes:

• Passing URL and capabilities as positional args
• Changing URL port without reason
• Incorrect browser name casing

5. You want to run tests on both Chrome and Firefox browsers using Selenium Grid. Which approach correctly sets up the test to run on both browsers sequentially using Python?

hard

A. Create one Remote WebDriver with both browser names in desired_capabilities at once

B. Start two Grid hubs, one for Chrome and one for Firefox, and connect separately

C. Run tests locally on Chrome and Firefox without Grid

D. Use a loop over a list of desired capabilities and create a Remote WebDriver for each browser inside the loop

Solution

1. Step 1: Understand how to run tests on multiple browsers with Grid

   Each Remote WebDriver instance connects to one browser session. To test multiple browsers, create separate instances.

2. Step 2: Evaluate options

   Use a loop over a list of desired capabilities and create a Remote WebDriver for each browser inside the loop correctly uses a loop to create Remote WebDriver for each browser sequentially. Create one Remote WebDriver with both browser names in desired_capabilities at once is invalid because desired_capabilities cannot hold multiple browsers at once.

3. Final Answer:

   Use a loop over a list of desired capabilities and create a Remote WebDriver for each browser inside the loop -> Option D

4. Quick Check:

   Loop over browsers, create Remote driver each time [OK]

Hint: Loop browsers, create Remote driver per browser session [OK]

Common Mistakes:

• Trying to set multiple browsers in one desired_capabilities dict
• Running tests locally instead of using Grid
• Starting multiple hubs unnecessarily