Jest Introduction for React Testing

Write a Jest Test for a React Component

Create a simple React component and write a Jest test that checks if it renders correctly.

Expected output: A passing Jest test verifying the component's output.

Hint: Use react-test-renderer for snapshot testing or React Testing Library for DOM testing.

Implement Mocking in a Jest Test

Write a Jest test that mocks a function dependency and verifies it was called.

Expected output: A test that passes and confirms the mock function was invoked.

Hint: Use jest.fn() to create a mock function and expect(mockFn).toHaveBeenCalled().

Jest is a JavaScript testing framework developed by Facebook. It is popular for React testing because it requires minimal configuration, supports snapshot testing, and provides powerful mocking capabilities.

Snapshot testing captures the rendered output of a React component and saves it. Future test runs compare the current output to the saved snapshot to detect unintended changes.

Mocking isolates the unit under test by replacing dependencies with controlled implementations, allowing tests to focus on specific behavior without external side effects.