text: const expect = require('expect');
  const maxDate = require('./maxDate.js');
  
  test('maxDate is a Function', () => {
    expect(maxDate).toBeInstanceOf(Function);
  });
  test('maxDate produces the maximum date', () => {
    const array = [
      new Date(2017, 4, 13),
      new Date(2018, 2, 12),
      new Date(2016, 0, 10),
      new Date(2016, 0, 9)
    ];
    expect(maxDate(array)).toEqual(new Date(2018, 2, 12));
  });
  