The regulatory minimum which must be demonstrated is between 20 and 25 knots (dependent upon the characteristics of the specific aircraft).
[that's per FAR25.237 - usual caveat as to variation in regs between authorities and with time, of course]
In order to minimize the impact on operations, most manufacturers will try to get somewhat more - even if we find that our highest 'demonstrated' crosswind didn't appear to be limiting, some operators or authorities may conservatively take the highest demonstrated condition as a limit, so it pays to do the best you can, within the limits of the test scheduling.
I'd say that most programmes would target 30kts, but would certainly go for more if they happened to get it, and won't waste an inordinate amount of test time trying to get 30kts if they already had, say, 28kts. So if you were to say ballpark 30-35kts demonstrated for most types, with the likely 'real' limit being somewhat higher, you won't be too far wrong.