testing-patterns

Create a getMockX function that returns default values and spreads a Partial overrides parameter, such as getMockUser({ role: 'admin' }). This keeps test data consistent, DRY, and easy to customize per test case.

Use jest.mock with a factory argument, for example jest.mock('utils/analytics', () => ({ Analytics: { logEvent: jest.fn() } })). Access the mock in tests via jest.requireMock to configure return values or assert calls.

Mock the generated hooks file with jest.mock('./GetItems.generated', () => ({ useGetItemsQuery: jest.fn() })), then use mockReturnValue to supply data, loading, and error states for each test scenario.

Use getBy when the element must exist, queryBy when asserting an element is absent (expect null), and findBy with waitFor for elements that appear asynchronously after data loads.

Asserting that a mock was called tests the mock rather than real behavior, creating brittle tests tied to implementation. Instead, assert on observable outcomes like rendered text or state changes visible to users.

Factories add indirection that may be unnecessary for trivial one-off values in a single test. They deliver the most value when the same data shape appears across multiple tests or requires consistent defaults.