Not necessarily valid for all countries:
https://www.legalmatch.com/law-library/article/what-is-assault.html
"Is It Necessary to Strike Someone In Order to Be Found Guilty of Assault?
A person does not necessarily need to strike someone in order to be found guilty of assault. In fact, the legal definition and elements of proof for assault do not ever mention any kind of physical contact—only the reasonable belief that harmful or offensive contact will be inflicted on the victim.
However, there are some acts that may offer stronger proof that an assault occurred. For example, getting in someone’s fact can be considered assault if the assaulter is being aggressive and doing things like screaming, spitting, or threatening to hit the other person with an object that they are holding (e.g., bat, beer bottle, fist, etc.).
On the other hand, getting in a friend’s face and pretending to slap them while both parties are laughing about it, will not constitute an assault."