How would you test an input that accepts integer ages from 18 through 60 inclusive?

Use equivalence classes and boundary values. Test representative valid input and the edges 18 and 60, plus invalid neighbors 17 and 61. Also test missing input, whitespace, nonnumeric text, fractional values, and out-of-range integers according to the contract. Verify both UI feedback and authoritative server validation. If age is calculated from a birth date, test date and timezone boundaries separately rather than treating it as a simple integer field. The expected result must come from agreed requirements, not from copying the current implementation’s behavior.