import Deferred from 'lib/deferred'; describe('Deferred', () => { test('resolve a deferred promise', () => { const deferred = new Deferred(); deferred.resolve(4); expect(deferred.promise).resolves.toBe(4); }); test('reject a deferred promise', () => { const deferred = new Deferred(); deferred.reject('error'); expect(deferred.promise).rejects.toBe('error'); }); });