This article is from the 3b1 computers FAQ, by John B. Bunch with numerous contributions by others.
The diagnostic floppy has a mode in it for the more experienced system tester. This mode allows the user to skip the menus and just specify the test to run. The diagnostic tests can be run repeatedly for testing intermittent hardware. The diagnostic output can be sent to a parallel printer for review later, and also for unattended testing (since the output can scroll off the screen rather easily).
To enter the expert mode, boot the diagnostic disk and type in "s4test" at the first menu prompt. The result is the following prompt:
expert>
From there you can type "?" for a "semi-verbose" command syntax, and a list of many of the tests. For more detail on what tests and subtests you can do, grab a nice file by Craig Votava (cmv@ihlpf.att.com) called "s4test.info.Z" from the OSU Archives.
 
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