I thought from vague memory that since running a SMART test is an internal routine, if you power it down and back up, the test should continue. After all, if you do a long test and any powerdown cancels it, that can be very impractical. If you want to cancel it, you can do so via command.
I started a long test and power cycles the device and checking status says
"The previous self-test routine completed without error or no self-test has ever been run."
And executing the -X command is also not very informative since it doesn't actually tell me whether there was any running test it canceled. It yields the same unspecific message every time.
I really want to do a full surface read test on a backup HDD but cannot depend on it running undisturbed for 12 hours.
I also ran an offline data collection but whenever I check it says it was interrupted by a host command, even though the drive isn't even mounted. (Activity LED on the dock starts coming on and stays on all the time, so that doesn't tell me whether it is actually running a test.)
Can any of this be related to running it in a USB dock?