YouTuber JerryRigEverything regularly performs scratch tests to many smartphones to try the durability of materials used on various components like the LED flash lens, camera lens, buttons, keys, and earpiece. He also performs burn tests to the display to somewhat simulate degradation of the pixels over time. And finally, a bend test is performed to test the phone's internal structure. Apple's infamous bendgate was a topic of controversy back when users began reporting that their iPhone 6 Plus became bent all of a sudden, just by either sitting on it or applying just intentional pressure....
Source: http://www.gsmarena.com/iphone_7_doesnt_actually_have_a_sapphire_lens_scratch_test_reveals-news-20561.php
