"Negative engineering" as described here is also especially challenging to test. Requires extraordinary backflips to construct reasonable approximations to the

"Negative engineering" as described here is also especially challenging to test. Requires extraordinary backflips to construct reasonable approximations to the edge conditions, corner cases, external factors, and unreasonable contingencies against which you're trying to defend. The same "Happy Path is just 20% of code" imbalance extends through test rig, tribal knowledge, and effort required. In some cases, 20% seems fantastically generous. IME preventing failures that only occur at heavy load or during other errors may be 95%+ of your effort and represent 99%+ of your "value add."