Some games work flawlessly even on wildly inaccurate emulators, others require exact emulation of subtle behaviour (and even then some still don't work).
Inputs do not work unless auto joypad polling is correct.
When riding the dragon Flammie (in the initial mid-altitude over-the-shoulder view, not the low-altitude overhead view or the whole-planet view), the Mode7 background will flicker black unless joypad auto polling is correct.
After starting a new game, walking to the red "Get Password" orb and pressing B will automatically dismiss the password screen unless joypad auto polling is correct.
Also, at the title screen, tapping B should open the main menu, but holding it for more than a few frames should automatically select "New Game". If the HVBJOY register does not correctly report whether auto joypad polling is active, this behaviour may be off in either direction (you can't tap B quickly enough to open the menu without selecting "New Game", or holding B will never select "New Game").
Not necessarily an emulation bug, but a hazard. Unlike other games with special hardware, there's no value in the internal header to tell you that a game accepts Sufami Turbo mini-cartridges. Instead, the emulator has to guess whether something "looks like" the Sufami Turbo base cartridge.
You could detect it by the size and hash of the ROM,
by the game's internal name (ADD-ON BASE CASSETE
),
or by the text at the beginning of the ROM (BANDAI SFC-ADX
).
You might be tempted
to use the four-letter game code in the extended header
to identify the cartridge,
but the basic header does not set the "has extended header" flag,
but beware:
this has the game code set to A9PJ
,
which is shared with the game
"Bishoujo Senshi Sailor Moon SuperS - Fuwafuwa Panic".
Sends random inputs even with no buttons pressed, unless auto joypad polling is correct.
Start button auto-unpauses unless auto joypad polling is correct.
Skips the intro animation, jumps straight to the title screen, and won't let you start the game unless auto joypad polling is correct.
Attract sequence ends early unless auto joypad polling is correct.
Inputs fire on their own, or menu items sometimes skipped unless auto joypad polling is correct.
This game hangs after showing the developer and publisher logos, before it gets to the title screen, unless auto joypad polling is correct.
Strangely, the European version and the Japanese version (which is just called Wolverine (Japan)) can work fine even if the USA version is broken.
On the main menu, holding the D-pad moves the cursor continuously instead of only once, unless auto joypad polling is correct.