When a woman cheats, other men will take semen into her vagina or body or clothes, and check the semen of that day with ice sperm test paper. As long as you are sure that you didn't leave it yourself, you can be sure that someone else left it. If it is in a woman's vagina, the semen will be kept for 3-5 days and can be detected when it flows out, but it will be gone after 7 days. Therefore, as long as you don't have sexual contact with her for more than seven days, your semen will not remain in her vagina, and if it is detected that the substance flowing out of her vagina or underwear contains semen components, it can be determined that the semen components belong to other men, that is, cheating.