smartctl: How to abort SMART test

Use

smartctl -X /dev/sda

to abort a running SMART test on /dev/sda.

Example output

smartctl 7.2 2020-12-30 r5155 [x86_64-linux-5.15.0-105-generic] (local build)
Copyright (C) 2002-20, Bruce Allen, Christian Franke, www.smartmontools.org

=== START OF OFFLINE IMMEDIATE AND SELF-TEST SECTION ===
Sending command: "Abort SMART off-line mode self-test routine".
Self-testing aborted!