Verify application behavior under slow network conditions

Preconditions (2)

Step 1: Open the application homepage in the browser

Step 2: Enable network throttling to simulate 3G slow network speed

Step 3: Reload the application page

Step 4: Observe the page load time and UI responsiveness

Step 5: Try to submit a form on the page

Step 6: Observe if the form submission completes successfully

✅ Expected Result: The application should load within a reasonable time under slow network, UI should remain responsive, and form submission should complete successfully without errors.

Automation Requirements - Selenium with Python

Assertions Needed:

Page load time is within acceptable threshold under throttled network

Form submission success message is displayed

No error messages appear during slow network

Best Practices:

Use Selenium WebDriver with Chrome DevTools Protocol to enable network throttling

Use explicit waits to handle dynamic page loading

Use clear and maintainable locators (id, name, or CSS selectors)

Measure and assert page load time programmatically

Automated Solution

Testing Fundamentals

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

# Setup Chrome driver with DevTools Protocol
options = webdriver.ChromeOptions()
service = Service()
driver = webdriver.Chrome(service=service, options=options)

try:
    # Enable network throttling to simulate slow 3G
    driver.execute_cdp_cmd('Network.enable', {})
    driver.execute_cdp_cmd('Network.emulateNetworkConditions', {
        'offline': False,
        'latency': 200,  # 200 ms latency
        'downloadThroughput': 500 * 1024 / 8,  # 500 kbps
        'uploadThroughput': 500 * 1024 / 8   # 500 kbps
    })

    start_time = time.time()
    driver.get('https://example.com')  # Replace with actual app URL

    # Wait for main element to load
    WebDriverWait(driver, 30).until(
        EC.presence_of_element_located((By.ID, 'main-content'))
    )
    load_time = time.time() - start_time

    # Assert page load time under 15 seconds for slow network
    assert load_time < 15, f"Page load took too long: {load_time} seconds"

    # Fill and submit form
    input_field = WebDriverWait(driver, 10).until(
        EC.element_to_be_clickable((By.ID, 'input-name'))
    )
    input_field.send_keys('Test User')

    submit_button = driver.find_element(By.ID, 'submit-btn')
    submit_button.click()

    # Wait for success message
    success_msg = WebDriverWait(driver, 15).until(
        EC.visibility_of_element_located((By.ID, 'success-message'))
    )

    assert 'success' in success_msg.text.lower(), "Success message not displayed"

finally:
    driver.quit()

This script uses Selenium WebDriver with Chrome DevTools Protocol to simulate a slow 3G network by setting latency and throughput limits.

We start by enabling network throttling, then load the application page and measure the load time.

We assert that the page loads within 15 seconds, which is reasonable for slow networks.

Next, we fill a form field and submit it, then wait for a success message to confirm the form submission worked.

Explicit waits ensure the script waits for elements to be ready before interacting, avoiding flaky tests.

Finally, the driver quits to close the browser cleanly.

Common Mistakes - 3 Pitfalls

Not enabling network throttling before loading the page

Using hardcoded sleep instead of explicit waits

Using brittle locators like absolute XPath

Bonus Challenge

Now add data-driven testing with 3 different network speeds: slow 3G, fast 3G, and 4G

Show Hint