Hunt The Edges With Boundary Values
Select boundary value tests around minimums, maximums, and threshold changes.
Middle values prove the path works; edge values prove the rule is right. Boundary value analysis focuses on edges because software frequently fails at thresholds. Humans write rules with words like "from," "through," "less than," and "at least." Code turns those words into operators like <, <=, >, and >=. A single wrong operator can pass every middle value while failing the exact point where money, access, or workflow changes. The mechanism is to test just below, exactly at, and just above each boundary. For the discount rule, the meaningful edges are $50 and $200. That suggests $49.99, $50.00, $50.01,…
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