export default function sleep(ms) {
  // TODO: return a Promise that resolves after ms milliseconds
  throw new Error('Not implemented');
}

import sleep from './file';

describe('sleep', () => {
  test('returns a promise', () => {
    const p = sleep(1);
    expect(p && typeof p.then).toBe('function');
  });

  test('resolves after at least the delay', async () => {
    const start = Date.now();
    await sleep(25);
    const elapsed = Date.now() - start;
    expect(elapsed >= 20).toBe(true);
  });

  test('resolves with undefined value', async () => {
    const out = await sleep(1);
    expect(out).toBe(undefined);
  });

  test('does not resolve synchronously', async () => {
    let resolved = false;
    const p = sleep(0).then(() => {
      resolved = true;
    });

    expect(resolved).toBe(false);
    await p;
    expect(resolved).toBe(true);
  });
});