How Selenium Works for Web Automation

Selenium is one of the most popular tools for web automation testing. It allows testers and developers to automate browsers for testing purposes or other repetitive tasks. To understand how Selenium works, we need to dive into its architecture and key components.

What Is Selenium?

Selenium is an open-source framework that automates web browsers. It supports multiple programming languages, including Java, Python, C#, and JavaScript, to write test scripts. Selenium is widely used for functional testing and supports all major browsers like Chrome, Firefox, Safari, Edge, and Internet Explorer.

Selenium Components

Selenium is not just a single tool; it’s a suite of tools designed to cater to different automation needs. Here are the core components:

Selenium Component	Details
Selenium WebDriver	Overview: Directly interacts with browsers via drivers to automate web applications. It supports multiple programming languages. Key Features: Cross-browser compatibility (Chrome, Firefox, Edge, Safari). Supports multiple languages (Java, Python, C#, etc.). Fast execution as it directly interacts with the browser. Works with automation frameworks like TestNG & Cucumber. When to Use: For functional and regression testing. When you need full browser automation. For scalable and maintainable automation frameworks.
Selenium IDE	Overview: A browser extension for **recording and playback** of test cases. Ideal for beginners and quick test creation. Key Features: No programming knowledge required. Record and replay actions easily. Can export tests to WebDriver scripts (Java, Python, etc.). Useful for exploratory testing. When to Use: If you are new to Selenium and want to learn automation. For quick bug reproduction and test case recording. When scripting is not needed (basic testing).
Selenium RC (Deprecated)	Overview: The older version of Selenium, which used JavaScript injection for browser automation. **Replaced by WebDriver**. Key Features: Worked across multiple browsers. Required a separate server to interact with browsers. Supported Java, Python, Ruby, PHP, etc. When to Use: ❌ Not recommended—use WebDriver instead. Only for legacy projects still running Selenium RC.
Selenium Grid	Overview: Allows **parallel execution** of test cases across multiple machines, browsers, and OS. Key Features: Hub-Node architecture for parallel execution. Cross-browser and cross-platform testing. Supports large-scale automation projects. Integrates well with CI/CD pipelines. When to Use: When running tests on **multiple environments simultaneously**. For **reducing execution time** in large test suites. To integrate with **Jenkins, CI/CD pipelines**.

Selenium WebDriver Architecture

Step	Action
1. Test Scripts	We write selenium code in IDE through which we ask the browser to perform some activity.
2. Selenium WebAPI	Since browser can not understand selenium code so, webdriver API interacts with Browser Driver via W3C Protocol.
3. W3C Protocol	Translates commands into HTTP requests. Note: Selenium4 onwards, W3C is being used and before this JSON wire protocol was being used.
4. Browser Driver	Receives the HTTP request and performs the action in the browser.
5. Browser Interaction	Executes the task, like navigating to a URL or interacting with web elements.

What Is the W3C Protocol?

The W3C WebDriver protocol is a standard that ensures consistent communication between browsers and Selenium WebDriver. Before this protocol, Selenium relied on JSON Wire Protocol, which sometimes caused inconsistencies due to browser-specific implementations. The W3C protocol eliminates these issues by providing:

• A standard for browser interaction.
• Improved stability across different browsers.
• Faster and more reliable test execution.

Example: Automating Google Search

import org.openqa.selenium.WebDriver;
import org.openqa.selenium.chrome.ChromeDriver;
import org.openqa.selenium.By;

public class GoogleSearchAutomation {
    public static void main(String[] args) {
        System.setProperty("webdriver.chrome.driver", "path-to-chromedriver");
        WebDriver driver = new ChromeDriver();
        driver.get("https://www.google.com");
        driver.findElement(By.name("q")).sendKeys("Selenium WebDriver");
        driver.findElement(By.name("q")).submit();
        driver.quit();
    }
}

Run above code

Conclusion

Selenium is a powerful tool for web automation, and understanding its architecture is crucial for mastering it. By leveraging its components and understanding the W3C protocol, testers can write reliable automation scripts.