it('should print empty string if no string given', () => {
      print();
      print('');

      expect(output.write).to.have.callCount(2);
      expect(output.write).to.have.been.calledWithMatch('');
      expect(output.write).to.have.been.calledWithMatch('');
    });
 it('should return a `thenAddNewLine` helper', () => {
   expect(print().thenAddNewLine).to.not.be.undefined;
 });