According to Economic Daily News, testing involves evaluating the use of OLED or Micro-LED display technology, "because the choice of either screen will affect the subsequent assembly methods".
Apple has also asked Foxconn to perform over 100,000 opening and closing tests.
"Similar tests for laptops require to be open and closed between 20,000 and 30,000 times," the report said on Tuesday.
Since foldable phones will be folded and unfolded far more frequently than laptops, the bearings inside them also need more rigorous testing.
The first foldable iPhone is expected to offer at least 8GB of RAM and 256GB of storage, and the baseline model may cost $1,499. It will reportedly be unveiled in November 2022.
This is not the first time Apple is rumoured to be working on a foldable iPhone model.
According to earlier reports, Apple ordered a batch of foldable displays from Samsung, suggesting that it is working on a foldable iPhone.