Docker containers for test execution in Selenium Python - Build an Automation Script

Run Selenium test inside a Docker container

Preconditions (3)

Step 1: Create a Dockerfile that installs Python, Selenium, and a browser driver

Step 2: Build the Docker image from the Dockerfile

Step 3: Run the Docker container with the test script mounted inside

Step 4: Execute the Selenium test script inside the container

Step 5: Observe the test execution and results

✅ Expected Result: The Selenium test runs successfully inside the Docker container and outputs the test result (pass/fail) to the console

Automation Requirements - Selenium with Python

Assertions Needed:

Verify the page title is as expected

Verify a specific element is present on the page

Best Practices:

Use explicit waits instead of sleep

Use Page Object Model for maintainability

Use Docker volumes to mount test scripts

Use headless browser mode for container execution

Automated Solution

Selenium Python

import unittest
from selenium import webdriver
from selenium.webdriver.chrome.service import Service
from selenium.webdriver.common.by import By
from selenium.webdriver.chrome.options import Options
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC

class TestGoogleSearch(unittest.TestCase):
    def setUp(self):
        chrome_options = Options()
        chrome_options.add_argument('--headless')
        chrome_options.add_argument('--no-sandbox')
        chrome_options.add_argument('--disable-dev-shm-usage')
        self.driver = webdriver.Chrome(service=Service('/usr/bin/chromedriver'), options=chrome_options)
        self.wait = WebDriverWait(self.driver, 10)

    def test_google_title_and_search_box(self):
        self.driver.get('https://www.google.com')
        # Assert page title
        self.assertIn('Google', self.driver.title)
        # Wait for search box presence
        search_box = self.wait.until(EC.presence_of_element_located((By.NAME, 'q')))
        self.assertTrue(search_box.is_displayed())

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

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

# Dockerfile content (to be created separately):
# FROM python:3.12-slim
# RUN apt-get update && apt-get install -y wget gnupg2 \
#     && wget -q -O - https://dl.google.com/linux/linux_signing_key.pub | apt-key add - \
#     && echo "deb [arch=amd64] http://dl.google.com/linux/chrome/deb/ stable main" > /etc/apt/sources.list.d/google-chrome.list \
#     && apt-get update && apt-get install -y google-chrome-stable \
#     && pip install selenium
# RUN wget https://chromedriver.storage.googleapis.com/114.0.5735.90/chromedriver_linux64.zip \
#     && unzip chromedriver_linux64.zip \
#     && mv chromedriver /usr/bin/chromedriver \
#     && chmod +x /usr/bin/chromedriver
# COPY test_script.py /tests/test_script.py
# WORKDIR /tests
# CMD ["python", "test_script.py"]

This test script uses Python's unittest framework with Selenium WebDriver.

In setUp, we configure Chrome to run in headless mode, which is important for running inside Docker containers without a display.

The test navigates to Google, checks the page title contains 'Google', and waits explicitly for the search box element to appear, then asserts it is visible.

The tearDown method closes the browser after the test.

The Dockerfile installs Chrome, ChromeDriver, and Selenium, then copies the test script inside the container and runs it.

This setup allows running the Selenium test fully inside a Docker container, ensuring consistent environment and easy test execution.

Common Mistakes - 4 Pitfalls

Using time.sleep() instead of explicit waits

{'mistake': 'Not running browser in headless mode inside Docker', 'why_bad': 'Docker containers usually have no display, so tests fail if browser tries to open GUI.', 'correct_approach': "Use headless browser options like '--headless' for Chrome."}

Hardcoding absolute paths for ChromeDriver

Not closing the browser after test

Bonus Challenge

Now add data-driven testing with 3 different URLs to verify their page titles inside the Docker container.

Show Hint