I'm sorta winging it here. I know how to design fast switching circuits, but I am no expert on reverse recovery time measurements. It turns out, as you might expect, that the techniques are different for small-signal diodes, e.g., 1N4148, than they are for multi-amp rectifiers. I don't think I want to tackle the high-current testing. Are you good with a relatively low current measurement? I think you will still get reverse current (you demonstrated it in the waveforms you posted), but the results probably won't agree with the datasheets.
Are you doing this out of curiosity, or for some explicit purpose?
Are you doing this out of curiosity, or for some explicit purpose?