I am currently working for a small startup. I was previously under contract, now I am working for equity (no pay). The thing is, there is not yet a signed agreement in place as the details are being worked out. I may finish development before the contract is ready.

I'm not currently under any contract or agreement, so the other party doesn't have any legal claim (that I know of) to the code I'm writing now, other than NDA (which just precludes me from cutting him out and releasing on my own). He already has the old code that I wrote under contract. I've made it clear to the other party that I won't submit the app or turn over the code until there's something signed to protect my interests. I've stopped pushing commits to the company repo (I'm now the only developer actively working on the project).

However, I would still like to send builds over TestFlight for feedback and testing purposes. The other party has access to the developer portal and iTunes Connect for code signing, etc. Things are amicable and I don't foresee getting burnt on this, but I'm not going to put myself in that position. My concern is that if I send a finished build via TestFlight, it could be extracted and submitted to the app store without my participation. They wouldn't have the source for future maintenance and updates, of course, but it could be reverse-engineered by another developer later working from the old code base.

Is this technically feasible at all? If so, is there a way I can send builds for testing while protecting my interests?