I had a ND today

[SideShow Bob]

I've had a stuck firing pin go full auto (luckily with only three rounds left in the magazine) due to a filthy pistol. And a slam fire from a protruding primer.
A hammer follow would be a mechanical problem that would have repeated itself while continuing shooting.
The empty chamber test is what should be done sparingly, usually after trigger work is done or for a suspected problem.

And yes, it is more likely to be found when the slide is dropped on an empty chamber.