testinglisted

# Testing Standards Language-agnostic defaults. Language-specific skills override where they conflict. **Golden Rule**: If you can't test it easily, refactor it. ## Structure and Naming - Arrange, act, assert: set up the data, execute the code, verify the result. One behavior per test. - Names state the expectation: `validateEmail returns false for invalid format`, not `it works` or `test user`. ## What to Test - **DO**: happy path; edge cases (boundaries, empty, null); error cases (invalid input, failures); business logic; public APIs. - **DON'T**: third-party libraries; framework internals; simple getters/setters; private implementation details. ## Coverage Coverage is an outcome of testing the right intersections, not a target to chase. Not every line, and not every one-liner, needs a test; a one-line pass-through does not. Cover each behavior and its real edges; a task's acceptance criteria are the floor. ## Principles - **Test behavior, not implementation**: focus on what, not how. Assert results, never that a mock was called with particular arguments: `expect(mock).toHaveBeenCalledWith(...)` pins procedure and goes red on a behavior-preserving refactor. - **Would it survive a refactor?** If a behavior-preserving refactor would turn the test red, it tests procedure; rewrite it to assert the result. Procedure-coupled tests lock in design flaws. - **Mock through injected boundaries**: dependency injection makes a hand-rolled fake (`{ findById: () => fixture }`) s