"Should I write an asm file for a hardware test, that maximizes the value of the test?"

Are you referring to data "value" or usefulness "value"? :)

I've posted the formula I use in FCEU before, but here it is again:

IRQ Clock Cycles=(DMA Clock Cycles) - (0x10-($4010 & 0x0F)) * 16 * (Length of sample in bytes)

"DMA Clock Cycles" refers to the number of CPU cycles between DMA(or expected from the outputted playback rate, at least).

Where "IRQ Clock cycles" is the number of CPU cycles at which time an IRQ is to be generated, after the 0x00->0x10 write to $4015. It is not 100% accurate, though. The playback frequency does seem to affect when the IRQ occurs(the games expect it this way, at least), so this should be factored into any tests that are run.