What is the test for a sexual harassment claim in a same-sex discrimination action?

biological gender: "[H]arassing conduct need not be motivated by sexual desire to support an inference of discrimination on the basis of sex. A trier of fact might reasonably find such discrimination, for example, if a female victim is harassed in such sex-specific and derogatory terms by another woman as to make it clear that the harasser is motivated by general hostility to the presence of women in the workplace. A same-sex harassment plaintiff may also, of course, offer direct comparative evidence about how the alleged harasser treated members of both sexes in a mixed-sex workplace. Whatever evidentiary route the plaintiff chooses to follow, he or she must always prove that the conduct at issue was not merely tinged with offensive sexual connotations, but actually constituted 'discrimina[tion] . . . because of . . . sex.'" (Oncale v. Sundowner Offshore Services, Inc. (1998) 523 U.S. 75, 80-81.)