Is there a test for them now? Can you give me a link or something? Over here we breed folds always with a Brit, so this doesn't become an issue. I hope it would be done much more elsewhere too (unless the test is reliable).Maybe that's why the Straights need a genetic test done before breeding. Perhaps some of them still carry the Fold gene although they appear Straight. l'm guessing, of course - l'm not a breeder. But it's very interesting.
Personally I would avoid breeding with a double fold, the kittens wouldn't get triple fold ears and that's how they really are supposed to be (in shows at least) and I think most of the 'unfolding' folds come from a breeding with a single or double fold cat. Unfortunately we have lots of BYBs here breeding folds, and their cats & kittens often have very weird semi-straight ears.