Apple’s first foldable phone just went through a heavy workout, and its hinge came out fine. Reviewer Joanna Stern folded and unfolded the $1,999 iPhone Duo more than 32,000 times. The hinge is the joint that lets the phone bend, and it’s the part most buyers worry about.

Stern shared the results in her iPhone Duo review. She ran the test over four nights with a custom-built folding machine. It worked at about 17 folds a minute for roughly eight hours each night. That is more than 8,000 folds a night. The phone wore a case the whole time.

What the test found

Stern worried the hinge might loosen as the folds piled up. A push-pull gauge, a tool that measures how much force it takes to move something, showed the opposite. The hinge took slightly more force to open after the test than before it.

In daily use, she said, “I really couldn’t feel a difference.”

That gives buyers something Apple hasn’t.…