ZX Spectrum timing test. 48K only.

btime (btime.tap) ULA border timing
stime (stime.tap) ULA screen timing
ulatest3 (ulatest3.tap) floating bus and contention

source (needs mktap, mktap.exe)

fusetest (by Philip Kendall; src), also contention, iocontention.
z80tests (by Mark Woodmass)
zexfix (zexall by Frank Cringle + J.G.Harston – errors = zexfix.tap)

« Qaop emulator

See also:

Harlequin project (ZX Spectrum clone) by Chris Smith.
Java Z80 comparison utils by Mikko Nummelin.

Some utils: