I can't stress enough the importance of testing. When Ezra and I created our makeshift egg dropper, we were fairly confident. We constructed the device out of what we could find in the dorm (a nalgene, some paper towels, a plastic bag, and some coat hangers) and came up with an unattractive, yet promising egg dropper. We walked over to Ezra's window, held the egg dropper out in all its glory and dropped it down one story. What ensued was a somewhat awkward, but seemingly reasonable descent for the dropper. But we were only given one egg for the whole project, so obviously we hadn't used it in the test. Since we had no egg in our test, we simply had to judge that the egg would probably survive. So we sent the egg and the dropper to class, confident that we were in good shape.
When the moment finally came to throw the dropper out the building, only to fall to the concrete three stories below, I just kind of threw and prayed. The loud thud that reached me seconds later let me know that either God didn't hear me, or we had made a pretty crappy egg dropper. Regardless, I learned that proper testing is necessary in order to be certain that your design will work. In testing our device, we lacked a crucial member of the egg dropper test: an actual egg. If we'd had multiple eggs to use in testing, we could have modified our device and possibly prevented the embarrassing drop.