Automated testing does not have a shortage of frameworks and Selenium is one of the most used frameworks to test web apps. Since it can compel browsers and perform other actions that mimic actual user activity, it is popular with developers and QA engineers. But that is not where Selenium’s power is: it is not only about test automation but also about the structure that makes this possible.
Selenium architecture is a perfect aspect that every test automation desires to know before they can unleash the full potential of the tool. In this blog, we will begin by discussing what is Selenium? Its architecture, including its parts and how it has been implemented today.
What Is Selenium?
With Selenium being the open-source testing framework and most adaptable framework for automation, it becomes easy to manage automation tasks such as filling up forms, pressing buttons, moving from one frame to another and more.
There are four main components of Selenium:
- Selenium WebDriver: It is the core of the system that talks directly to the browsers in order to actually carry out the testing.
- Selenium IDE: A software used in recording tests and playback.
- Selenium Grid: A tool to execute tests across several machines or to be able to execute the same tests concurrently.
- Selenium RC (Remote Control): A class that was utilized before WebDriver but is no longer in operation today.
The Anatomy of Selenium Architecture
To explain Selenium’s functionality, let’s discuss its architecture in detail step by step. Selenium WebDriver works with a client-server model. This means it is made of a client, which is the test script, and a server, which is an actual browser that has been opened.
1. The Selenium Client
The Selenium client is actually the executable code to be run, which is written in one of the supported programming languages. WebDriver – this means that it describes to WebDriver what to do, such as open a browser, click a button, type some text, and so on. The client communicates with WebDriver using a set of Application Programming Interfaces, which is Selenium.
The most commonly used Selenium client languages are:
- Java
- Python
- C#
- Ruby
- JavaScript (Node.js)
Once the Selenium WebDriver client receives the commands, it sends them to the WebDriver server.
Now, some might ask, What is Selenium WebDriver? It is a key component of the Selenium framework that facilitates the interaction between test scripts and the browser. It directly controls the browser by translating test commands into actions that the browser understands.
2. The WebDriver Server
WebDriver is created to work directly with the browser, and this is when all the action takes place. WebDriver should not be misconceived as a browser automation tool in its own right or standing alone. In this case, it serves as a middleman between the client, which is the test script, and the browser.
When a test script puts out commands to WebDriver, WebDriver is able to map those commands to equivalent browser actions. It sends these commands to the browser driver, which will then execute these steps on the browser.
There are browser-specific drivers, such as:
- ChromeDriver for Google Chrome
- GeckoDriver for Mozilla Firefox
- EdgeDriver for Microsoft Edge
- SafariDriver for Apple Safari
These browser drivers are specific to their respective browsers and are responsible for executing the commands received from WebDriver.
3. Browser Driver
The browser driver helps in bridging the communication between the WebDriver and the browser. WebDriver sends a command to click on a button, then the browser driver will transform the command into a set of events that are recognizable by the browser, including mimicking a mouse click on the button in the DOM tree.
4. The Browser
Finally, the browser executes the commands sent by the browser driver. The browser is where the test’s actual execution takes place. It renders the web pages, handles user interactions, and displays the test results. During the execution of automated tests, the browser operates as it normally would, but all interactions are driven by WebDriver commands.
The Modern Selenium Workflow
The modern Selenium workflow involves writing test scripts, interacting with the WebDriver, and executing tests on browsers. Here’s a high-level view of this process:
- Test Script: The developer writes a test script using a supported language (Java, Python, etc.), specifying browser actions (click, type, navigate).
- WebDriver Client: The test script communicates with the WebDriver client (through APIs).
- WebDriver Server: The WebDriver server translates commands into browser-specific instructions.
- Browser Driver: The browser driver converts WebDriver commands into actions that the browser can understand.
- Browser: The browser executes the commands, and results are returned to WebDriver.
- Results: The result of the automated test is shown, and the test script can also interpret the results of the test (pass/fail).
It demonstrates where Selenium is able to remove much of the complication behind browser automation, providing developers and QA engineers with an environment that enables them to write out test scripts with precision.
Selenium Grid and Parallel Execution
One of the limitations of running tests on a single machine is that tests can take much time to run, especially when running through a large test suite. Selenium Grid is an influential feature and is used to distribute test cases across several other machines together for parallel runs. It can greatly minimize the time taken to execute tests and enhance test coverage at the same time.
Here’s how Selenium Grid works:
- Hub: The central server that manages the test execution. It receives test requests from WebDriver clients and routes them to the appropriate node.
- Node: The machines connected to the hub that actually run the tests. Every node can launch one or several browsers and operating systems to perform cross-browser and cross-OS testing.
Selenium Grid is vital for scaling test automation because using it allows teams to run tests on various browsers and operating systems at once.
Modern Implementation Strategies
With the basic structure of Selenium now clear, let’s go over some of the current trends of Selenium implementation that make it even more effective and fast.
1. Use of Page Object Model (POM)
Page Object Model (POM) is a design pattern that follows the approach to maintain reusable scripts and easy-to-handle scripts. In POM, each web page is modeled as a class and to access/utilize that web page, methods are created. This way, test scripts don’t need to overrun the same code to interact with the elements in a page.
For example, a test script that tests a login functionality would create a LoginPage object with methods like enterUsername(), enterPassword(), and submitLogin(). The test script would then call these methods to perform actions on the page.
This pattern is of great benefit in the following ways: first, it slows down redundancy; second, it makes the tests easier to manage and maintain; and third, it permits the reuse of code pieces in several other tests.
2. Data-Driven Testing
When using data-driven testing it implies that the same tests are performed with different data input. It is most beneficial when it comes to form testing or any function that needs data input in which the same steps have to be performed in which data has to be different.
It implies that through the integration of Selenium with Apache POI or the use of CSV files, databases, or, indeed, any other data source, data-driven testing is supported. It enables the testers to repeat the same test as many times as possible to enhance robustness and reliability.
3. Headless Browsers
By automating the test in a CI/CD pipeline, we can identify any defects at the early stage of application development as well as maintain the confidence level of the application being released at any one time.
Selenium supports headless testing with browsers like Chrome and Firefox. By running tests in headless mode, teams can execute tests faster, save resources, and integrate them into CI/CD pipelines seamlessly.
4. Integration with CI/CD Tools
Integrating Selenium tests with CI/CD tools like Jenkins, GitLab CI, or CircleCI allows automated tests to run every time there’s a change in the codebase. It allows developers to ensure that new changes do not ‘break’ known working solutions; it also offers immediate feedback to the developers.
By automating the test in a CI/CD pipeline, we can identify any defects at the early stage of application development as well as maintain the confidence level of the application being released at any one time.
5. Cloud Testing Services
Using cloud testing platforms benefits organizations by enhancing the testing or development overflow with ease without having to maintain an environment and having to maintain physical devices.
One such platform is LambdaTest. It is an AI-powered test execution platform that lets you perform manual and automated tests across 3000+ browser and OS combinations.
Such platforms help to manage the large infrastructure needed to run the huge volume of test automation on browsers, operating systems, and devices. These services work with Selenium and help you execute your tests on cloud-based environments rather than emulating the environments.
In addition to enhancing the scalability and flexibility of test automation, LambdaTest provides seamless integration with various automation testing frameworks and tools, allowing teams to run tests across a wide range of browsers, operating systems, and real devices.
These services eliminate the need for managing local test environments and infrastructure, enabling teams to focus on writing and optimizing test scripts.
By utilizing cloud environments, developers and testers can conduct more comprehensive tests, ensuring cross-browser compatibility and delivering faster, more reliable results.
This approach not only reduces overhead costs but also accelerates the testing process, making it a valuable asset for any modern test automation strategy.
6. Parallel Execution
As mentioned earlier, Selenium Grid allows for parallel execution, but modern implementations also leverage cloud-based services to run tests on multiple devices and browsers simultaneously. This parallel execution reduces test time and allows teams to cover a broader range of devices and configurations, ensuring that applications work across all environments.
7. Integration with Version Control Systems
One of the most effective strategies for modern Selenium implementations is integrating with version control systems like GitHub, GitLab, Jenkins and more to ensure that tests are always in sync with the latest version of the application, providing real-time feedback as changes are made.
Conclusion
Selenium supports all browsers and scripts by accepting interaction through the client-server model, and by supporting scripting through several programming languages, Selenium has made browser automation powerful and scalable. These tactics, which include Page Object Model, Data Driven Testing, Headless Browsers, and CI/CD Integrations, help the teams to make their tests more efficient and easy to maintain.
In addition, Selenium Grid, together with cloud testing services, enables the teams to extend the test automation and execute the necessary tests faster, as well as cover more territory. Relying on these strategies, Selenium remains the effective and absolutely inalienable tool for web testing in different platforms and environments despite the constantly changing landscape of web automation.
