The white wingtips in juveniles is not an indicator of S or s. I have seen it in the Golden Laced Wyandottes I raised years ago. Most often it goes away, but sometimes it is still there in the adult plumage. If you want to test a black, blue, or splash male for S/s, cross it on a silver. If all the female offspring end up with some gold or red feathers in the hackle the male tested is ss which is homozygous for sex linked gold. If some females have red and some have white, the tested male is split for S and s. If all the females have white in the hackle, the tested male was SS, homozygous for sex linked silver. If some of the males have white in the hackle and some have amber, the tested male was split for S and s. If all the males have amber, the male was ss (homozygous for sex linked gold). If all the males have white in the hackle, the tested male was SS (homozygous for sex linked silver). Females inherit only one copy of S or s, so cannot be split like the males can be. Obviously you would need a fair sized sample to do the test.