The same like any other relationship - have it in writing, with penalties specified, and besides the contract, do basic due diligence with your supplier. China

The same like any other relationship - have it in writing, with penalties specified, and besides the contract, do basic due diligence with your supplier. China is not some lawless backwater, despite the fake news bogeyman in recent years. You can get played out just the same by a supplier in Belgium - like any business relationship, you take steps to mitigate the risk, but nothing is ever 100% iron-clad. You should still get a written agreement. *Edit: "Who else do you supply to" is a very common part of interacting with a supplier, and most of the time they are chomping at the bit to share their "famous customer list" with you. In fact, some suppliers even have pages on their website listing who their "authorised resllers/distributors" are. Having a chat with any of the others helps, and like any business relationship, it's a human relationship with some trust involved. You back things up with legal protections, but in the end, business is about the human aspect of things.