What defines a boundary test?

• A. A test with typical input
• B. A test to ensure correct error messages
• C. A test that checks values at the edge of the valid input range
• D. A test that measures run time

Answer: (C)

Boundary testing focuses on edge values of the input range to catch problems that happen at the limits. When inputs are defined within a range, it’s essential to check the smallest and largest valid values, as well as values just inside and just outside those limits, to see how the system handles them. For example, if a program accepts 1 to 100, boundary tests would look at 1 and 100 (the edges) and nearby values like 2 and 99, plus outside values like 0 or 101 to ensure proper rejection or handling. This helps reveal off-by-one errors, input validation gaps, and how limits are enforced.

This is why the option describing boundary values is the best choice. Other options address testing normal, typical input, or focus on error messages or performance, which don’t specifically target the edge of the valid input range.