equivalence-partitioning-bva

Turn a parameter's valid/invalid ranges into a systematic set of test cases by partitioning the input space into equivalence classes and probing the boundaries between them, where bugs disproportionately cluster. Use eagerly whenever the user needs test cases for numeric ranges (age, quantity, price, days), string length constraints, date/time windows, or enumerated sets — especially when they say "what test cases should I write for this", "what are the edge cases", "boundary values", "off-by-one", or describe a method with documented min/max constraints on its parameters. Also trigger when they mention validation logic for a range-constrained input and aren't sure what to check beyond the happy path. If the problem is really about combinations of many independent parameters rather than the boundaries of one, the scenario-design skill can route to combinatorial-testing instead.