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March 03, 2025 00:40
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Selenium Testing & Debugging Cheatsheet

A quick reference for testing and debugging web applications using Selenium, covering common commands, debugging techniques, and best practices.

Core Selenium Commands

Basic Navigation

driver.get(url)

Loads a new web page.

driver.current_url

Returns the URL of the current page.

driver.title

Returns the title of the current page.

driver.refresh()

Refreshes the current page.

driver.back()

Navigates to the previous page in history.

driver.forward()

Navigates to the next page in history.

Element Interaction

element.send_keys(value)

Simulates typing into an element.

element.click()

Clicks on an element.

element.clear()

Clears the text of an input or textarea element.

element.get_attribute(name)

Gets the value of an element’s attribute.

element.text

Gets the visible text of the element.

element.is_displayed()

Checks if the element is currently displayed.

Finding Elements

driver.find_element(By.ID, id)

Finds an element by its ID.

driver.find_element(By.NAME, name)

Finds an element by its name attribute.

driver.find_element(By.CLASS_NAME, class_name)

Finds an element by its class name.

driver.find_element(By.TAG_NAME, tag_name)

Finds an element by its tag name.

driver.find_element(By.LINK_TEXT, link_text)

Finds a link by its exact text.

driver.find_element(By.PARTIAL_LINK_TEXT, partial_link_text)

Finds a link by a partial match of its text.

Advanced Selenium Techniques

Explicit Waits

WebDriverWait(driver, timeout).until(EC.presence_of_element_located((By.ID, 'element_id')))

Waits until an element is present in the DOM.

WebDriverWait(driver, timeout).until(EC.visibility_of_element_located((By.ID, 'element_id')))

Waits until an element is visible.

WebDriverWait(driver, timeout).until(EC.element_to_be_clickable((By.ID, 'element_id')))

Waits until an element is clickable.

WebDriverWait(driver, timeout).until(EC.text_to_be_present_in_element((By.ID, 'element_id'), text))

Waits until specific text is present in the element.

WebDriverWait(driver, timeout).until(EC.title_contains(title))

Waits until the page title contains specific text.

WebDriverWait(driver, timeout).until(EC.alert_is_present())

Waits until an alert is present.

Handling Alerts and Popups

alert = driver.switch_to.alert

Switches the context to the currently active alert.

alert.accept()

Accepts the alert (clicks ‘OK’).

alert.dismiss()

Dismisses the alert (clicks ‘Cancel’).

alert.send_keys(text)

Sends text to the alert prompt.

alert.text

Gets the text of the alert.

driver.switch_to.default_content()

Switches back to the main document content.

Executing JavaScript

driver.execute_script(script, *args)

Executes JavaScript in the current browser context.

script: The JavaScript code to execute.
*args: Any arguments to pass to the script.

Example: driver.execute_script("window.scrollTo(0, document.body.scrollHeight);")

Scrolls to the bottom of the page.

Example: driver.execute_script("arguments[0].click();", element)

Clicks on a specific element using JavaScript.

Debugging Techniques

Common Exceptions

NoSuchElementException: Element not found.

  • Verify the locator is correct.
  • Ensure the element is present in the DOM.
  • Use explicit waits to wait for the element to appear.

TimeoutException: Element not found within the specified time.

  • Increase the timeout value.
  • Verify the element is actually present.
  • Check for dynamic content loading issues.

ElementNotInteractableException: Element is not clickable or visible.

  • Ensure the element is visible and enabled.
  • Check for overlapping elements.
  • Scroll the element into view.

StaleElementReferenceException: Element is no longer attached to the DOM.

  • Re-locate the element.
  • Avoid storing element references for long periods.

Debugging Strategies

  1. Take Screenshots: Capture the state of the browser at the point of failure.

driver.save_screenshot(“error.png”)
```
  1. Inspect the DOM: Use browser developer tools to inspect the DOM structure and element attributes.

  1. Add Logging: Log important events and variables to track the test flow.

import logging
logging.basicConfig(level=logging.INFO)
logging.info(“Clicking the button”)
element.click()
```

  1. Use Debugging Tools: Utilize Python’s pdb or other debugging tools to step through the code.

import pdb; pdb.set_trace()
```

Selenium Grid

Selenium Grid allows running tests in parallel across different browsers and operating systems. It consists of a Hub and Nodes.

Hub: Central point that receives test requests and distributes them to available nodes.

Nodes: Registers with the Hub and provides the browsers and OS environments for running tests.

Best Practices

Code Maintainability

  1. Use Page Object Model (POM): Create classes representing web pages, encapsulating locators and actions. This promotes reusability and reduces code duplication.
  1. Use Data-Driven Testing: Parameterize tests with data from external sources to improve coverage and maintainability.
  1. Avoid Hardcoded Waits: Use explicit waits instead of hardcoded time.sleep() calls to improve test reliability.

Test Reliability

  1. Run Tests in Isolation: Ensure tests do not depend on each other to avoid cascading failures.
  1. Use Test Fixtures: Set up and tear down test environments to ensure consistent starting conditions.
  1. Handle Dynamic Content: Use robust locators and explicit waits to handle dynamic content and AJAX requests.

Parallel Execution

  1. Use Selenium Grid: Distribute tests across multiple machines and browsers to reduce test execution time.
  1. Parallel Test Runners: Utilize test runners like pytest-xdist or nose-parallel to run tests in parallel within a single machine.