An edge case is a problem or situation that occurs only at an extreme (maximum or minimum) operating parameter. In software development, an edge case is a type of software bug that wont be a widespread issue. Instead, it only affects a small number of users, devices, or can only be reproduced under unique circumstances. Edge cases can be expected or unexpected, and they may not have been foreseen during the design phase. Non-trivial edge cases can result in the failure of an object that is being engineered. In programming, an edge case typically involves input values that require special handling in an algorithm behind a computer program. Developers must validate such cases through unit testing to ensure the program behaves correctly. Edge cases are important to consider because they can be exploited by hackers, who make a habit of discovering edge cases.

Corner cases are different from edge cases, even though they are commonly referred to as the same thing. A corner case is when multiple parameters are simultaneously at extreme levels, and the user is put at a corner of the configuration space. For instance, if both times were set to 10 minutes and the heat power was at 5, or if the time was set to 0.5 minutes and heat to 1.