Why are Selenium tests running slow or timing out?

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Several factors can contribute to Selenium tests running slow or eventually timing out. Investigating and addressing these issues is essential for maintaining the efficiency and reliability of your Selenium test automation.

TestingBot has been providing a cloud-based Selenium grid since 2012. During those years, we've gathered knowledge about improving the reliability of Selenium tests.

Network Latency

Slow network connections or high latency can impact the speed at which Selenium interacts with the browser. Every command is sent as a HTTP(s) command to a Selenium node. If there is latency between you and the node, this might cause tests to lag.

To improve this, you should use a reliable and fast network connection. At TestingBot we provide an optimised Selenium grid with high availability and low latency.

Heavy Browser Operations

Performing heavy operations in the browser, such as handling a large number of elements or executing complex JavaScript code might slow down test execution. If you are testing a webpage that requires WebGL or (Web)GPU, make sure you test on a machine that has the necessary resources, such as a NVIDIA GPU or a modern VGA card.

Large Test Suites

Running a large number of tests in a single suite can lead to a slower execution, because the CPU or RAM might become a bottleneck. Long running tasks may also affect the performance of tests, as it might introduce memory leaks.

TestingBot suggests to keep tests as small as possible, without any dependency on eachother. Take advantage of the increased parallelization that TestingBot provides to run tests across multiple machines simultaneously.

Inefficient Waits

Incorrect or inefficient use of waits (implicit or explicit) can introduce unnecessary delays in your test. If you need to add a delay, make sure it's always checking for an expected condition. For example, you can have your test script wait for an element to appear in the DOM.

Try to avoid adding sleep statements to your code, instead use an optimized wait strategy such as an implicit or explicit wait. Good usage of wait strategies will reduce the chance of test flakiness.

Unhandled JavaScript Alerts or Pop-ups

Unhandled JavaScript alerts or unexpected pop-ups can halt test execution in certain situations. Make sure you implement proper handling for JavaScript alerts and handle expected pop-ups in your test script.

Outdated Selenium or Browser Versions

Using outdated versions of Selenium WebDriver or browsers may lead to compatibility issues and performance problems. Make sure you keep the Selenium version you are using up-to-date. You'll benefit from the latest improvements and bugfixes made by the Selenium open-source community.

TestingBot has all these best practices regarding Selenium implemented in its Selenium Grid. Ready to give it a try? Sign up for free!

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