PAGE 41: How Selenium Webdriver Works

There are 2 ways of explaining how Selenium WebDriver works:

• easy
• technical

Lets see how easy is the first one.

It uses an analogy with taxi driving.

Selenium WebDriver drives a browser the same way a taxi driver drives a cab.

In taxi driving, there are typically 3 actors:

• the client; he tells the taxi driver where he wants to go and how to get there

• the taxi driver; he executes the client's requests; the taxi driver sends his own requests to the car

• the car; the car executes the taxi driver's requests

The client gets to the destination through dialogues that happen between the client - taxi driver and taxi driver - car.

In test automation with Selenium WebDriver (and other tools), there are 3 actors as well:

• test engineer that writes the automation code; the automation code sends requests to the browser driver component

• the browser driver component; it executes the test engineer requests; it sends its own request to the browser

• the browser; it executes the browser driver requests

So this is the analogy:

1. the test engineer is like a taxi client

1. the browser driver is like a taxi driver

1. the browser is like a taxi

The technical explanation is not using analogies.

Like most technical explanations, there are no photos either :(

When the automation script is executed, the following steps happen:

• for each Selenium command, a HTTP request is created and sent to the browser driver

• the browser driver uses a HTTP server for getting the HTTP requests

• the HTTP server determines the steps needed for implementing the Selenium command

• the implementation steps are executed on the browser

• the execution status is sent back to the HTTP server

• the HTTP server sends the status back to the automation script