well,
once again, look at the wiki. there's a lot of info.
http://wiki.nesdev.com/w/index.php/Emulator_tests
the first one under CPU
is nestest, which does not require a PPU.
Quote:
fairly thoroughly tests CPU operation. This is the best test to start with when getting a CPU emulator working for the first time. Start execution at $C000 and compare execution with a log from Nintendulator, whose CPU works (apart from some details of the power-up state).