How possible the human with XX genome have testis?
(in Langman's Medical Embryology wrote the 70 percent of hermaphrodite with testis have xx karyotype.)

This happens (rarely) if you get strange cross over between X and Y chromosomes at meiosis during spermatogenesis such that SRY (the sex determining gene normally on the short arm of Y) gets onto an X chromosome. Simplistically SRY can be thoughts of as switching on male development, so if a sperm bearing SRY on an X chromosome combines with an egg (always bears an X), the result can be an offspring with XX karyotype that expresses SRY and shows at least some "male" development.

Some info on this in humans   

https://en.wikipedia.org/wiki/XX_male_syndrome