Clock.test.native.jsx

import React, { StrictMode } from 'react';
import {
  render,
  flushMicrotasksQueue,
} from 'react-native-testing-library';
import sinon from 'sinon';
import App from '../examples/native-clock/App';

describe('Clock App', () => {
  const clock = sinon.useFakeTimers();
  const { getByText, unmount } = render(
    <StrictMode>
      <App />
    </StrictMode>,
  );
  // flush the inital didMount effect
  flushMicrotasksQueue();

  const clearIntervalSpy = sinon.spy(global, 'clearInterval');

  afterAll(() => {
    clock.restore();
    clearIntervalSpy.restore();
  });

  test('should update to display the current time every second', () => {
    expect(getByText('12:00:00 AM')).toBeDefined();

    clock.tick(2000);
    expect(getByText('12:00:02 AM')).toBeDefined();

    clock.tick(8500);
    expect(getByText('12:00:10 AM')).toBeDefined();
  });

  test('should clean up the interval timer when the component is unmounted', () => {
    unmount();
    expect(clearIntervalSpy.callCount).toBe(1);
  });
});