Once you receive your samples, it is time to perform a visual inspection and a functioning test. The main focus here is to make sure that the sample will lift up to the standards that you set for your product. For example, at The Lashes, we emphasize on our lashes being ultra lightweight, having all day comfort, and the ability to be worn over 15 times. So during our stress test, we put the lashes against all of these value points in order to make sure that they meet or exceed the bar that we set for the product.
For the most part, if you're going with the ODM route, where you're just placing your brand on an existing product, you don't need to do as long of a stability test as you do for OEM products, because the manufacturer would have already done all the tests on the product already. Now let's walk through how to improve your sample based on external data. My usual path is to find reviews of my competitors and pay close attention on the reviews on the product, especially the negative ones.
Your competitor's shortcomings are opportunities for your product in the market. Finally, the most traditional and solid way is to invite people to try out your product. Make sure you are selective in who you choose and only pick people that fit your target audience. Pay close attention to how they use your product, any difficulties they have, and observe the user experience with your product. Through these findings, you should be able to tweak your samples a bit further to fit the final version that you're comfortable with.