An edge case is a problem or situation that occurs only at an extreme (maximum or minimum) 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 ...

. For example, a stereo speaker might noticeably distort audio when played at maximum volume, even in the absence of any other extreme setting or condition. An edge case can be expected or unexpected. In

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 ...

, the process of planning for and gracefully addressing edge cases can be a significant task, and yet this task may be overlooked or underestimated. Non-trivial edge cases can result in the failure of an object that is being engineered. They may not have been foreseen during the

design A design is a plan or specification for the construction of an object or system or for the implementation of an activity or process or the result of that plan or specification in the form of a prototype, product, or process. The verb ''to design'' ...

phase, and they may not have been thought possible during normal use of the object. For this reason, attempts to formalize good engineering standards often include information about edge cases.

Software engineering

In programming, an edge case typically involves input values that require special handling in an

algorithm In mathematics and computer science, an algorithm () is a finite sequence of rigorous instructions, typically used to solve a class of specific Computational problem, problems or to perform a computation. Algorithms are used as specificat ...

behind a computer program. As a measure for validating the behavior of computer programs in such cases,

unit tests In computer programming, unit testing is a software testing method by which individual units of source code—sets of one or more computer program modules together with associated control data, usage procedures, and operating procedures&mda ...

are usually created; they are testing boundary conditions of an algorithm,

function Function or functionality may refer to: Computing * Function key, a type of key on computer keyboards * Function model, a structured representation of processes in a system * Function object or functor or functionoid, a concept of object-oriente ...

method Method ( grc, μέθοδος, methodos) literally means a pursuit of knowledge, investigation, mode of prosecuting such inquiry, or system. In recent centuries it more often means a prescribed process for completing a task. It may refer to: *Scien ...

. A series of edge cases around each "boundary" can be used to give reasonable

coverage Coverage may refer to: Filmmaking * Coverage (lens), the size of the image a lens can produce * Camera coverage, the amount of footage shot and different camera setups used in filming a scene * Script coverage, a short summary of a script, wri ...

and confidence using the assumption that if it behaves correctly at the edges, it should behave everywhere else. For example, a function that divides two numbers might be tested using both very large and very small numbers. This assumes that if it works for both ends of the magnitude spectrum, it should work correctly in between.

References

Engineering concepts Usability Technical communication Software testing {{Engineering-stub

Software engineering

See also

References