New advanced feature: Destructive Disk Test (experimental)
The new disk test is much faster, but experimental. Feedback appreciated, send an email or open an issue if you've tried it and it didn't work right - or even if it did work as expected.
Download the AppImage file for most Linux desktops, mark it as executable in your filemanager and run it. Those who use Windows may either want to download and run the CapacityTester exe file or the CapacityTester zip archive and extract all files in the same, new folder before opening the exe file.