Editing Corner case

{{short description|Engineering situation}}
{{Refimprove|date=August 2019}}

In [[engineering]], a '''corner case''' (or '''pathological case''') involves a problem or situation that occurs only outside normal operating [[parameter]]s—specifically one that manifests itself when multiple environmental variables or conditions are simultaneously at extreme levels, even though each parameter is within the specified range for that parameter.

For example, a loudspeaker might distort audio, but only when played at maximum volume, maximum [[Bass (sound)|bass]], and in a [[Humidity|high-humidity]] environment. Or a [[Server (computing)|computer server]] may be unreliable, but only with the maximum complement of 64 [[Microprocessor|processors]], 512 [[Gigabyte|GB]] of [[Computer memory|memory]], and 10,000 signed-on [[User (computing)|users]]. The investigation of corner cases is of extreme importance as it can provide engineers with valuable insight into how corner case effects can be mitigated. In the case where automotive radar fails, corner case investigation can possibly tell engineers and investigators alike what may have occurred.<ref>{{Cite journal|last=Chipengo|first=Ushemadzoro|date=2018|title=From Antenna Design to High Fidelity, Full Physics Automotive Radar Sensor Corner Case Simulation|journal=Modelling and Simulation in Engineering|volume=2018|pages=1–20|doi=10.1155/2018/4239725|doi-access=free}}</ref>

Corner cases form part of an [[engineer]]'s lexicon—especially an engineer involved in testing or [[debugging]] a complex system. Corner cases are often harder and more expensive to reproduce, test, and optimize because they require maximal configurations in multiple dimensions. They are frequently less-tested, given the belief that few product users will, in practice, exercise the product at multiple simultaneous maximum settings. Expert users of systems therefore routinely find corner case anomalies, and in many of these, errors.

The term "corner case" comes about by physical analogy with "edge case" as an extension of the "[[flight envelope]]" metaphor to a set of testing conditions whose boundaries are determined by the 2<sup>n</sup> combinations of extreme (minimum and maximum) values for the number ''n'' of variables being tested, ''i.e.'', the total [[parameter space]] for those variables. Where an edge case involves pushing one variable to a minimum or maximum, putting users at the "edge" of the [[Configuration space (physics)|configuration space]], a corner case involves doing so with multiple variables, which would put users at a "corner" of a multidimensional configuration space.

==See also==

* [[Black swan theory]], a metaphor describing a major surprising event that is often inappropriately rationalised after the fact
* [[Edge case]], an issue that occurs only at a single extreme (maximum or minimum) parameter
* [[Linear programming]]
* [[Random testing]]
* [[Fuzzing]]

==References==
{{reflist}}

{{DEFAULTSORT:Corner Case}}
[[Category:Engineering concepts]]
[[Category:Software testing]]