I have a question regarding water leaking issue from the ceiling.

Am interested in a property but it has leaking problem from the ceiling in one of the room - agent said she will get the owner to sign a form to submit to developer to rectify this problem. At the moment, have yet to sign any agreement or made a booking because worried that if i make an earnest deposit to secure the property and IF there is still leaking issue after I buy the property, it will be quite problematic on our side? I don't know if the developer will want to cover up with paint work just to 'rectify' the problem

So how do I ascertain that the leaking issue is rectified properly after that - do i need to go down to check after a rainy day?