Step 1: Find a sweet as rooftop. Make sure it has lots of different levels, staircases, ladders etc…
Step 2: Ensure that your lens is working condition, perform a series of test shots to be sure it has no pre-existing damage. In this case study, a manual 50mm lens was used.
Step 3: Allow your lens to roll out of your bag and fall down a step ladder, (4Ms should be sufficient height). As it falls, listen for multiple bangs and crashes on the steps to ensure it takes numerous impacts on different sides of its body, preferably including the glass on both sides.
Step 4: Shit, your, pants. Rush down, mount the lens in question to your camera and perform a second round of test shots.
Step 5: Determine what damage has been done as a result of the fall, if any. In this case study, no damage was found.
Step 6: ???
Step 7: PROFIT!