You can test it at home. Have one of you forget your home wifi, then put their phone on airplane mode (but turn wifi back on). The other one then goes into airplane mode with wifi on, and turns on their hotspot. If the person who forgot their home wifi can connect, it will work on board too.
If you don't want the hassle of forgetting your home wifi, go to a coffee shop and just have one of you connect to the wifi, then turn off cellular data on both and try the hotspot.