engineering Engineering is the use of scientific method, scientific principles to design and build machines, structures, and other items, including bridges, tunnels, roads, vehicles, and buildings. The discipline of engineering encompasses a broad rang ...

, a corner case (or pathological case) involves a problem or situation that occurs only outside normal operating

parameter A parameter (), generally, is any characteristic that can help in defining or classifying a particular system (meaning an event, project, object, situation, etc.). That is, a parameter is an element of a system that is useful, or critical, when ...

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 Bass or Basses may refer to: Fish * Bass (fish), various saltwater and freshwater species Music * Bass (sound), describing low-frequency sound or one of several instruments in the bass range: ** Bass (instrument), including: ** Acoustic bass gui ...

, and in a high-humidity environment. Or a computer server may be unreliable, but only with the maximum complement of 64 processors, 512 GB of

memory Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembered ...

, and 10,000 signed-on

users Ancient Egyptian roles * User (ancient Egyptian official), an ancient Egyptian nomarch (governor) of the Eighth Dynasty * Useramen, an ancient Egyptian vizier also called "User" Other uses * User (computing), a person (or software) using a ...

. 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. Corner cases form part of an

engineer Engineers, as practitioners of engineering, are professionals who invent, design, analyze, build and test machines, complex systems, structures, gadgets and materials to fulfill functional objectives and requirements while considering the l ...

's lexicon—especially an engineer involved in testing or

debugging In computer programming and software development, debugging is the process of finding and resolving ''bugs'' (defects or problems that prevent correct operation) within computer programs, software, or systems. Debugging tactics can involve in ...

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 2ⁿ 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, a corner case involves doing so with multiple variables, which would put users at a "corner" of a multidimensional configuration space.

References

{{DEFAULTSORT:Corner Case Engineering concepts Software testing

See also

References