How do you define infidelity (cheating)?
Having an affair?
Hooking up after a drunk night?
Paid sex with an escort/prostitute
Happy ending massage?
French kissing someone?
Staying active on a dating site?
Flirting?
Sexting?
All above are cheating. But for sexting I can say in watsapp we sometime send adult jokes to friends. It is not cheating. But it hurts our partner's feeling its better to refrain that.