Most brick and mortar chains in the UK have a buying policy that requires you to prove your goods are fit for purpose before they'll put it on the shelves and risk hurting their brand. I imagine most of Europe operates similarly.
They will generally require suppliers to send examples of the range before being allowed in store, and they will test or examine a representative selection first. They'll probably do basic safety and legality tests too. As a new supplier you can expect your products to be subject to random checks over the coming months. After a period of good track record you will become a trusted supplier and subject to fewer, or perhaps no, checks.
Amazon should do the same. That they are big or that they are online is no excuse not to.