A highly accelerated stress test (HAST) is a type of test used to find out how reliable a product is. It is usually done to new products or electronics to see how long they can last when put under very stressful conditions. During the test, the products are exposed to extreme temperatures, high levels of humidity, and other types of pressure that can make the item work harder than normal. This test helps to make sure the product will still work for its intended purpose even when put through a tough situation.