我在让Chai的expect.to.thrownode.js应用程序进行测试时遇到问题。测试会因引发的错误而不断失败，但是如果我将测试用例包装在try和catch中并断言所捕获的错误，它将起作用。

难道expect.to.throw不喜欢的工作，我认为它应该还是什么？

it('should throw an error if you try to get an undefined property', function (done) {
  var params = { a: 'test', b: 'test', c: 'test' };
  var model = new TestModel(MOCK_REQUEST, params);

  // neither of these work
  expect(model.get('z')).to.throw('Property does not exist in model schema.');
  expect(model.get('z')).to.throw(new Error('Property does not exist in model schema.'));

  // this works
  try { 
    model.get('z'); 
  }
  catch(err) {
    expect(err).to.eql(new Error('Property does not exist in model schema.'));
  }

  done();
});

失败：

19 passing (25ms)
  1 failing

  1) Model Base should throw an error if you try to get an undefined property:
     Error: Property does not exist in model schema.