Antimatter Doesn't Have Anti-Inertial Mass

Any force applied to a positron would then move it in the opposite direction of that force whether it's a gravitational force or electromagnetic force. If you think about it like an electron repels another electron right because they have both have negative charge now if you have an electron and a positron they would normally attract each other because they have opposite charges but then if it has negative inertial mass then it actually maybe flips that force and it does repel. It could be kind of a way to prove that antimatter doesn't have anti-inertial mass is that you know if you have  an electron it gets attracted to an anti-electron which means that it doesn't have