testing▌

Write tests first, watch them fail, then implement minimal code to pass. \n \n Follows the red-green-refactor cycle: write a failing test, verify it fails correctly, implement minimal code to pass, then refactor while keeping tests green \n Requires deleting any production code written before tests exist; no exceptions for \"reference\" or \"adaptation\" \n Emphasizes watching tests fail as proof they actually test the right thing; tests that pass immediately prove nothing \n Covers common ratio