text: import test from 'ava';
  import { Just, Nothing } from '../../src/Maybe';
  
  test('returns false on the Just instance', t => {
    const j = Just(10);
  
    t.false(j.isNothing);
  });
  
  test('returns false on the Nothing instance', t => {
    const n = Nothing();
  
    t.true(n.isNothing);
  });
  