Several biologists (Jerry Coyne, Carole Hooven, Colin Wright) have noted that gametes “define” sex. For practical reasons (and other reasons as well), sex tests should not include checking for gametes (in my opinion). For males, this would only be moderately hard. For females, it would require highly invasive surgery. Of course, ultrasounds could be used to look for ovaries or testes without highly invasive surgery. However, ultrasounds are still moderately difficult (I had one for reasons having nothing to do with sex tests). I suggest Buccal smears (cheek swabs). They are fast, cheap, and highly reliable, with ultrasounds as a rarely used backup. Of course, Swyer’s persons don’t have functional ovaries. However, they do have fallopian tubes and a uterus. With medical help (IVF), they can have babies. In my opinion, they are female. However, an ultrasound would find nothing for CAIS. Are CAIS persons male or female? Not clear to me. Mosaic persons are another strange case (to me at least). The good news is that Swyer’s syndrome and CAIS and mosaicism are quite rare.