Testing is not only about software. It’s about hardware as well. We may await high reliability from our devices, especially if it’s high-end ones. It should have no damage and continue to work when we accidentally drop it, spill a cup with hot coffee or even sit on it.
Big HW vendors, of course, have their own hardware testlabs where they test all similar cases before mass production starts, and adjust design & materials accordingly. They use various mechanical tools to simulate load, drops, spills, etc. plus monitoring devices to collect results.
Watch these incredible videos how Dell do HW testing of their notebooks.