Boundary Value Analysis with Examples

A boundary separates neighboring partitions. It may be numeric, chronological, spatial, ordinal, or based on a count. Common examples include minimum password length, maximum upload size, subscription expiry, pagination limits, rate thresholds, and supported viewport widths.

The requirement must state whether the edge is included. “Up to 10 files” normally includes 10; “less than 10” does not. Ambiguous language is itself a review finding that should be resolved before expected results are finalized.

One-value boundary coverage exercises each boundary value. Two-value coverage exercises the boundary and its closest neighbor in the adjacent partition. For a valid integer range of 1 through 100, that produces 0 and 1 at the lower boundary, then 100 and 101 at the upper boundary.

In real work, teams often add the nearest valid interior value as well when off-by-one risk is high. The important point is to name the chosen coverage rather than call any collection of near-edge values “boundary testing.”

The closest neighbor depends on the domain. For whole numbers it may be one unit. For currency it may be one cent. For timestamps it may be the smallest supported precision. For file sizes it may be one byte—or the interface may round values and require tests at both displayed and stored boundaries.

Boundaries can also occur between states: before and after expiry, just below and at a free-shipping threshold, or the last item on one page and the first item on the next.