App.test.tsx

import { TEST_DEFAULT_DATE } from '#testing/constants';
import { renderWithProviders } from '#testing/render';
import { screen } from '@testing-library/react-native';
import React from 'react';
import { Text, View } from 'react-native';
import App from './App';

it('finds rendered text', () => {
  renderWithProviders(<App />);

  expect(
    screen.getByText(/Welcome to the Joconde Bootstrap App/),
  ).toBeOnTheScreen();
});

test('works with fake timers', async () => {
  let loading = true;
  let data: string | undefined = undefined;

  jest.setSystemTime(Date.now());
  const Suspending = () => {
    // eslint-disable-next-line jest/no-conditional-in-test
    if (loading)
      throw Promise.resolve('result').then((result) => {
        data = result;
        loading = false;
      });
    return <Text>{data}</Text>;
  };

  const screen = renderWithProviders(
    <View>
      <React.Suspense fallback={<Text>Loading</Text>}>
        <Suspending />
      </React.Suspense>
    </View>,
  );

  expect(await screen.findByText('result')).toBeOnTheScreen();
});

it('uses fake timers', () => {
  const callback = jest.fn();

  setTimeout(callback, 1000);

  expect(callback).not.toHaveBeenCalled();

  jest.advanceTimersByTime(1000);

  expect(callback).toHaveBeenCalledWith();
});

describe('date is mocked', () => {
  it('uses a mocked date', () => {
    expect(new Date(Date.now()).toISOString()).toBe(TEST_DEFAULT_DATE);
  });

  it('allows overriding the mock in a given test', () => {
    jest.setSystemTime(1244);

    expect(Date.now()).toBe(1244);
  });

  it("and then it's back to the global mock in the next test", () => {
    expect(new Date(Date.now()).toISOString()).toBe(TEST_DEFAULT_DATE);
  });
});

describe('timezone is mocked', () => {
  it('is in the Europe/Paris timezone', () => {
    // On our computers this is obviously true, but in the CI it would fail without the mock
    expect(new Date().getTimezoneOffset()).toBe(-60);
  });
});