tests-jest-frontendlisted

# Frontend unit tests: Jest Write and run frontend component and unit tests using Jest conventions. The unit-test script is the project's own (`test`/`test:unit`) or `npx jest`. - 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). - **Targeted rerun:** the test file path or `--testPathPattern` as the path filter, plus `-t`/`--testNamePattern` to match by test name. - **Discovery:** `npx jest --listTests` (files only). A file the list misses has a `testMatch` problem. - **Skip mechanism:** `it.skip`/`describe.skip`, `xit`.