Why is NoSuchSessionException Faced in Selenium?

Anushree Chatterjee

Imagine you’re on a phone call with a friend.

Your friend’s phone abruptly ends the call as its battery suddenly depletes and shuts down. However, you’re unaware of this and continue talking, expecting a response. When you get no reply, you’re confused and realize the call has been disconnected.

This analogy perfectly sums up the reason for a NoSuchSessionException in Selenium.

What is NoSuchSessionException?

When the browser session is no longer active, attempting to call methods triggers the NoSuchSessionException.

In the preceding example, your persistent endeavor to communicate parallels your script’s effort in conveying commands to the browser via Selenium. Similar to the unexpected ending of a browser session or the loss of connection between WebDriver and the browser, your friend’s phone shutting down provides an equivalent scenario.

You experience surprise upon discovering the call disconnected; similarly, when your Selenium script attempts interaction with an already non-existent browser session, it throws back a NoSuchSessionException.

Reasons for NoSuchSessionException

Here are some common reasons leading you to this exception.

Issues with browser stability or user intervention

When the browser closes suddenly by itself or when a person shuts it down during a script in action, Selenium loses its connection with the browser, and this particular error happens.

Challenges with WebDriver initialization or termination

If the WebDriver setup is not correct or it stops suddenly, the current session may be affected.

The problem might come up when the WebDriver file is not there or does not match the version of the browser you have now.

Delays or extended operation times

Occasions where operations take an unusually long time or network delays occur might lead to a session timing out, which triggers this error.

Mistakes in the Selenium script

Attempting to interact with non-existent elements on a webpage through the script can interrupt the session.

Problems with simultaneous Selenium sessions

Operating several Selenium sessions at the same time without adequate control can cause conflicts in the sessions, leading to this error.

Incompatibility between browser and WebDriver

The error may also arise if there’s a mismatch between the browser’s version and the WebDriver being used.

Test environment complications

Issues in the testing environment, like a lack of necessary resources or improper configuration, may also result in the loss of a session.

Resolution for NoSuchSessionException

When it comes to managing this exception, there are a couple of ways for you to do this.

Make sure that WebDriver and browser are up-to-date

This is a common cause and most avoided, too. It can save you from a lot of unnecessary issues.

Be particular during WebDriver initialization

Make sure the WebDriver is correctly initialized before you start running the tests. This involves setting the correct path to the WebDriver and choosing the right driver for your browser.

Do not close browser instances manually

During the execution of your Selenium script, do not manually close the browser. Let the script manage the opening and closing of the browser.

Clean up after tests

Ensure that your script properly closes and disposes of the WebDriver instance after the tests are complete. This cleanup is crucial to prevent leftover processes from interfering with new test runs.

Besides these precautions, you should always use try-catch blocks to make your test case failings graceful with proper messages.

Try a better alternative with testRigor

Though there are ways to prevent NoSuchSessionException in Selenium, there are a host of reasons why you would be better off opting for other alternative test automation tools.

One such alternative is testRigor, a generative AI-powered intelligent test automation tool. Using it, you can automate test cases across various platforms like the web, mobile, API, and even desktop. This can be done in the comfort of plain English, as writing tests here do not involve using programming languages. You need not manage the sessions, browsers, or any dependencies. Directly select the environment and start testing quickly with its powerful integrations with test management, infrastructure management, and CI/CD tools.

testRigor does not rely on unstable XPath/CSS locators; instead, it uses testRigor locators to identify elements. This approach works as a human would. You just write the element’s name as you see it on the UI, with no frills or complexities.

check that page contains "Login"

The tool uses AI to identify the elements and page contexts. Further, you can construct intricate test cases that involve working with table data; these could include tasks such as email authentication and much more.

If your test scripts do encounter errors, they don’t leave you hanging with complex exception names. testRigor offers you more than a mere English explanation of your issues; it provides screenshots, even detailed technical logs, and execution recordings to pinpoint precisely what went wrong.

You can further look at testRigor’s offerings over here and even create a free account to try them out.

“We spent so much time on maintenance when using Selenium, and we spend nearly zero time with maintenance using testRigor.”

Keith Powe VP Of Engineering - IDT