Web applications sometimes appear to lack smoothness when the the application isn't keeping up with the refresh yet. This is also referred to as jankiness.
According to jankfree.org:
Jank is any stuttering, juddering or just plain halting that users see when a site or app isn't keeping up with the refresh rate. Jank is the result of frames taking too long for a browser to make, and it negatively impacts your users and how they experience your site or app.
To see an example, go to https://googlechrome.github.io/devtools-samples/jank/.
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This feature is available only for testing web applications with the Google Chrome browser.
Enable your script to measure Jankiness
- Add the necessary capabilities to execute a performance script, as described in Measure Page Load Performance using Test Automation.
- Unlike the page load performance, it is up to the script to decide when to measure jankiness. Add the following to your script at the right places you want to measure jankiness:
For details, see Test Command.
The full Performance Report provides you access to all jank metrics as well as area charts showing the Frames Per Second (FPS) CPU and Heap memory used during the jank test