What are boundary values in testing?

Boundary values in testing refer to the values that lie on the edges of input categories, such as the minimum and maximum limits of input ranges. This concept is vital in software testing because many errors often occur at the boundaries of input domains rather than in the center. For example, when testing an application that accepts age as input, the boundary values would be the lowest age (e.g., 0) and the highest age that the application can handle (e.g., 120 if that's the defined maximum).

Testing these boundary conditions helps identify problems that users might encounter when input values are at the extreme ends of valid ranges. It ensures that the application can handle these critical limits correctly and provides reliable outputs. Through this method, testers can effectively pinpoint potential errors or oversights in code logic that may not be evident with inputs that are well within the normal range.