tests-jest-frontendlisted

# Frontend unit tests: Jest Write and run frontend component and unit tests using Jest conventions. Run them with the project's own unit-test script if it defines one (e.g. a `test` / `test:unit` npm script that invokes Jest); otherwise invoke Jest directly (`npx jest`). The `Frontend test command` slot is the **e2e** command — don't use it for unit tests. - Test files are typically co-located with their source file (`Button.test.tsx` next to `Button.tsx`) or collected under `src/__tests__/`. Check the project's `jest.config.*` (or the `jest` key in `package.json`) for the actual `testMatch` / `testPathPattern` before creating a new file. - Use `@testing-library/react` (`render`, `screen`) with `userEvent` from `@testing-library/user-event` for component tests; use plain `jest.fn()` / `jest.spyOn()` for unit mocks and `jest.mock()` for module mocks. - Prefer queries that reflect how users perceive the UI (`getByRole`, `getByLabelText`, `getByText`) over implementation-detail selectors (`getByTestId`, CSS class). - On re-verify, run only the failing test(s) — pass the test file path or `--testPathPattern` — not the whole suite.