Please identify yourself for future reference. I'm not sure why we are taking anonymous questions in a private community. That said...
I believe you need to frame your thinking differently. Consider the use case carefully, you are essentially going to have customers incorporate your product into the software they deliver to their customers so of course they will do a extensive testing before delivering their software with your protection incorporated into their product.
I would instead run your own tests to insure it's as high quality as possible as a first step, if you haven't already. I assume you would have already done this but without knowing it's worth being explicit. If you've actually done your own testing extensively, then you have to sell it as a solution. I don't know of a software company that will just "beta test" a product for the benefit of a vendor.
There has to be something uniquely beneficial about your product that induces them to want to use it - again, I have no idea why your's is better over what's available but this is what will make them want to use your product. If you can get that interest, then you will have the beginnings of a relationship.
Be right up from with interested prospects that you are looking for early adopters and will work them to develop a testing approach in the project which will allow them to extensively test your approach in their QA process. Let them know they won't "accept" the software until it's past their internal tests, and won't pay until it's completed all acceptance tests.
In the end, this is about a risk/reward scenario and it's a common one for any software startup. How do I get first sales of a product? Answer: Your value proposition has to be worth the risk. Then it's about mitigating the risks, which in your case (and most cases) is about testing and careful, phased deployment which you plan out with the customer.
But they won't do the testing unless they want to use the product. And the real test will be in the field with actual installs at their clients sites. They may do some beta testing with existing clients who they have friendly relationships with so they are confident before the actually embed your protection into their product more broadly.
Make sense? Fyi, this is actually a sales challenge, not a technical one...