Our advice
Select and develop test methods with the customer

Make your customer the "owner" of the method: this is the best way to ensure that the choice of method will last. You'll certainly need to write it up and send it to your customer for approval. If the method comes back to you "stamped" with your customer's seal of approval, you'll have guaranteed that it won't be changed during the course of the project (except by modifying the evaluation scales, if necessary). This will reassure you that your customer considers you to be a reference in the field of your technical relations. This can be an important phase in establishing a relationship of trust that is always beneficial, even in the industrial world.