Oh, one more thing. You need to have a brain to design the testing scheme.
Parts that can be bitten off or broken off should be tested as such. If someone fails to see a potential threat and does not test it, then a flaw will get through.
This may have happened with the magnet. Somebody thought the magnet was tablet-shaped and could be swallowed safely (like wheels from a toy car) and passed out the intestinal system. They failed to account for the possibility of two magnets being swallowed and attracting each other in the intestinal tract.
On the other hand, if the toy only has one magnet, it is probably not that big of a deal.