Re: Customer terminated contract before completion - any obligations re certification
Advise the customer in writing (and keep a copy) that the current works have not been tested due to termination of contract, and that anybody working on the installation in future must perform a full test as no guarantee can be given on incomplete works. I would also get them to sign something that expresses the fact that THEY are terminating the contract.
Hope they're paying you for what's been done.
If you have done any testing or certification at all, make sure you keep hold of it but don't bother giving a copy to the customer. When you test you are obliged to make and keep a record of it, but there is no obligation to give a copy to the customer.