Selenium

What is Selenium?

Selenium is an open-source automation framework used to automate web browsers. It allows you to interact with web applications just like a real user—clicking buttons, filling out forms, navigating pages, and even running automated tests.

It supports multiple programming languages like Python, Java, C#, and JavaScript and works with popular browsers like Chrome, Firefox, Edge, and Safari.

Use Case: Selenium is mainly used for web application testing, web scraping, and automating repetitive browser tasks.

How Does Selenium Work?

Selenium works by interacting with web elements through WebDriver, which acts as a bridge between your automation script and the web browser.

Basic Workflow of Selenium:

1. Write a script using Python (or another language).

2. Use Selenium WebDriver to control the browser.

3. Launch the browser (e.g., Chrome, Firefox).

4. Perform actions (click, type, navigate, etc.).

5. Validate results (check page title, element text, etc.).

6. Close the browser when done.

Where is Selenium Used?

🔹 Web Application Testing – Automate UI testing. 🔹 Web Scraping – Extract data from web pages. 🔹 Automating Repetitive Tasks – Auto-login, form filling, etc. 🔹 CI/CD Pipelines – Used in DevOps workflows. 🔹 Performance Monitoring – Automate page load testing.

1. Install Selenium

Open your terminal or command prompt and install Selenium using pip:

pip install selenium

2. Download WebDriver

Selenium needs a driver to control the browser. Download the appropriate driver for your browser:

• Chrome: Chromedriver

• Firefox: Geckodriver

• Edge: Microsoft Edge WebDriver

Ensure the driver is placed in a directory accessible by your system PATH.

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Step 3: Launch a Browser with Selenium

Once installed, let's open a browser using Selenium.

Example: Open Google in Chrome

from selenium import webdriver

# Path to chromedriver (if not in PATH, specify the absolute path)
driver = webdriver.Chrome()

# Open a website
driver.get("https://www.google.com")

# Close the browser
driver.quit()

🔹 .get(url): Opens the given URL. 🔹 .quit(): Closes the browser.

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Step 4: Interact with Web Elements

To interact with elements on a webpage, we need locators. The most common locators are:

• ID

• Name

• Class Name

• Tag Name

• CSS Selector

• XPath

Example: Search in Google

from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.common.keys import Keys

driver = webdriver.Chrome()
driver.get("https://www.google.com")

# Find the search box using name locator
search_box = driver.find_element(By.NAME, "q")

# Type in the search box and press Enter
search_box.send_keys("Selenium Python" + Keys.RETURN)

# Close the browser after 5 seconds
import time
time.sleep(5)
driver.quit()

🔹 find_element(By.NAME, "q"): Finds the search box by name attribute. 🔹 send_keys("Selenium Python"): Inputs text into the search box. 🔹 Keys.RETURN: Simulates pressing the Enter key.

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Step 5: Handling Clicks and Buttons

Many websites require interaction with buttons and links.

Example: Clicking a Button

driver.find_element(By.NAME, "btnK").click()

Here, we use .click() to click the Google search button.

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Step 6: Handling Dropdowns and Forms

Some websites have dropdown menus and forms that need interaction.

Example: Selecting from a Dropdown

from selenium.webdriver.support.ui import Select

dropdown = Select(driver.find_element(By.ID, "dropdown_id"))
dropdown.select_by_visible_text("Option 1")

🔹 Select(driver.find_element(By.ID, "dropdown_id")): Finds the dropdown element. 🔹 .select_by_visible_text("Option 1"): Selects the option with the given text.

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Step 7: Handling Alerts and Pop-ups

Web applications sometimes display pop-ups or alerts.

Example: Handling an Alert

alert = driver.switch_to.alert
alert.accept()  # Clicks OK

🔹 .switch_to.alert: Switches to the alert window. 🔹 .accept(): Clicks the OK button.

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Step 8: Working with Frames and Windows

Some websites have iframes or open new windows.

Switching to an iFrame

driver.switch_to.frame("iframe_id")

Switching Between Windows

driver.switch_to.window(driver.window_handles[1])

🔹 .switch_to.frame(): Switches to an iframe. 🔹 .switch_to.window(): Switches to another tab.

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Step 9: Implicit and Explicit Waits

Selenium can wait for elements to load before interacting.

Implicit Wait

driver.implicitly_wait(10)  # Waits up to 10 seconds

Explicit Wait

from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC

wait = WebDriverWait(driver, 10)
element = wait.until(EC.presence_of_element_located((By.ID, "element_id")))

🔹 implicitly_wait(): Waits for elements to appear. 🔹 WebDriverWait(): Waits for a specific condition.

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Step 10: Running Tests in Headless Mode

You can run Selenium without opening a browser (useful for automation).

Example: Headless Chrome

from selenium.webdriver.chrome.options import Options

options = Options()
options.headless = True
driver = webdriver.Chrome(options=options)

driver.get("https://www.google.com")
print(driver.title)
driver.quit()

🔹 options.headless = True: Runs the browser in the background.

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Step 11: Running Selenium Tests in PyTest

If you want to write automated tests, use pytest.

Example: Writing a Test Case

import pytest
from selenium import webdriver

@pytest.fixture
def driver():
    driver = webdriver.Chrome()
    yield driver
    driver.quit()

def test_google_title(driver):
    driver.get("https://www.google.com")
    assert "Google" in driver.title

Run the test using:

pytest test_script.py

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Step 12: Scraping Data with Selenium

Although BeautifulSoup is used for web scraping, Selenium can also extract data.

Example: Scraping Titles

titles = driver.find_elements(By.TAG_NAME, "h3")
for title in titles:
    print(title.text)

🔹 find_elements(): Finds multiple elements. 🔹 .text: Extracts text from elements.

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Step 13: Running Selenium on a Cloud Server (CI/CD Integration)

If you want to run Selenium tests automatically in the cloud, you can use:

• Selenium Grid

• Dockerized Selenium

• Cloud Testing Platforms (e.g., BrowserStack, Sauce Labs)

Example Docker command to run Selenium Grid:

docker run -d -p 4444:4444 --name selenium-grid selenium/standalone-chrome

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Step 14: Advanced Selenium Concepts

• Capturing Screenshots

driver.save_screenshot("screenshot.png")

• File Upload

driver.find_element(By.ID, "upload").send_keys("/path/to/file.txt")

• Mouse Actions

from selenium.webdriver.common.action_chains import ActionChains
action = ActionChains(driver)
action.move_to_element(element).perform()

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Example: Open Google and Search for "Selenium Python"

pythonCopyEditfrom selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.common.keys import Keys

# Start a browser session
driver = webdriver.Chrome()

# Open Google
driver.get("https://www.google.com")

# Find the search box and type a query
search_box = driver.find_element(By.NAME, "q")
search_box.send_keys("Selenium Python" + Keys.RETURN)

# Wait and close browser
import time
time.sleep(5)
driver.quit()

🔹 WebDriver interacts with Google Chrome. 🔹 Finds elements using locators like By.NAME. 🔹 Simulates user input (send_keys() and RETURN).