What is Selenium? Does it support multiple users?

Selenium is a programming tool used to automate the browser — simulating a real user by opening windows, going to URLs, clicking buttons, filling in forms, etc. Selenium is primarily used for test automation, but can also be used for other things.

Selenium is available as a library for most popular programming languages, including Java, JavaScript, TypeScript, C#, Python, Ruby, PHP, etc.

It is also referred to as Selenium WebDriver, because there were two different projects (Selenium & WebDriver) which did similar things and eventually merged. Selenium uses the WebDriver protocol (a W3C standard now) to communicate over the network via a REST API. This allows for remote automation,

There are other tools associated with Selenium, including Selenium Grid — which enables remote execution of automation and Selenium IDE — which allows you to record and play back automated steps without writing code, and has (limited) ability to to export from Selenium IDE to code that can run independent.

Selenium IDE does not support multiple users, but scripts can be exported and shared from one user to another.

Selenium Grid allows for parallel remote execution of Selenium scripts, which allows multiple people (or tests) to execute tests at the same time.

The concept of “supporting multiple users” does not really make sense in terms of Selenium as an open source development tool or coding library.

It would be like saying:
“Does Microsoft Word support multiple users?” or
“Does the Java programming language support multiple users?”

In the case of Microsoft Word, every user that has the program can use it, but collaboration is (primarily) done outside of the tool. With proprietary software like Microsoft Word, each user may need a license to run their own copy of the application, but Selenium is open source, so does not require the purchase of any license to use.

And as a programming library, any number of users can reference Selenium in their own code and execute it. Users can run multiple automated tests (or other scripts) at once — if they write their program to run in parallel.

But in order to maximize parallel execution (for single or multiple users) you need to have a remote Selenium grid. There is an open source grid that anyone can deploy, but there are also commercial services the host Selenium Grid with additional tools at a cost. These companies include Sauce Labs, BrowserStack, LambdaTest, and Applitools. Each company has their own policy about multiple users, and of the ones I mentioned, they all support multiple users in their own way.

This post is based on a question asked on Quora at: https://www.quora.com/What-is-Selenium-Does-it-support-multiple-users

When should you use JavaScriptExecutor in Selenium?

When you want to execute JavaScript on the browser :)

This was my answer to a question on Quora


JavaScriptExecutor is an interface that defines 2 methods:

in Java (and similarly in C#):

Object executeScript(String script, Object... args)


Object executeAsyncScript(String script, Object... args)

which take as an argument a string representing the JavaScript code you want to execute on the browser and (optionally) one or more arguments. If the second argument is a WebElement it will apply the script to the corresponding HTML element. Arguments are added to the JS magic arguments variable which represents the values passed to a function. If the code executed returns a value, that is returned to your Selenium code

Each driver is responsible for implementing it for the browser.

RemoteWebDriver implements it as well.

But when *you* as a Selenium user want to use JavaScriptExecutor is when you assign a driver to the base type WebDriver, which does not implement it.

in this case, you cast your driver instance (which really does implement executeScript() and executeScriptAsync().

For example

WebDriver driver = new ChromeDriver();  

// base type ‘WebDriver’ does not define executeScript() although our instance that extends RemoteWebDriver actually does implement it.

// So we need to cast it to ‘JavaScriptExecutor’ to let the Java compiler know.

JavaScriptExecutor js = (JavaScriptExecutor) driver;

js.executeScript(“alert(‘hi from Selenium’);”

if you keep your instance typing, you do not need to cast to JavaScriptExecutor.

RemoteWebDriver driver = new RemoteWebDriver(url, capabilities);  

// information about our type is not lost so the Java compiler knows our object implements executeScript()

WebElement element = driver.findElement(By.id(“mybutton”));

driver.executeScript(“arguments[0].click();", element);

// in the above case it adds the element to arguments and performs a click() event (in JavaScript in the browser) on our element

String htmlsnippet = driver.executeScript(“return document.querySelector(‘#myid’).outerHTML” , element);

// this time we use native JavaScript on the browser to find an element and return its HTML, bypassing Selenium’s ability to do so.

The above two examples illustrate ways you can accomplish in JavaScript what you would normally use Selenium for.

Why would you do this?

Well, sometimes the driver has a bug, or it can be more efficient (or reliable) to do in JavaScript, or you might want to combine multiple actions in 1 WebDriver call.