断言针对抛出的错误对象

Question

我有一个抛出对象的函数，如何断言正确的对象是在开玩笑呢？

it('should throw', () => {

  const errorObj = {
    myError: {
      name: 'myError',
      desc: 'myDescription'
    }
  };

  const fn = () => {
    throw errorObj;
  }

  expect(() => fn()).toThrowError(errorObj);
});

https://repl.it/repls/FrayedViolentBoa

Answer 1

如果您要测试自定义错误的内容（我认为这是您要尝试的操作）。您可以捕获错误，然后执行断言。

it('should throw', () => {
 let thrownError;

 try {
   fn();
 }
 catch(error) {
  thrownError = error;
 }

 expect(thrownError).toEqual(expectedErrorObj);
});

正如Dez所建议的，如果您不抛出javascript Error对象的实例，则toThrowError函数将不起作用。但是，您可以通过装饰错误对象的实例来创建自定义错误。

例如

let myError = new Error('some message');
myError.data = { name: 'myError',
                 desc: 'myDescription' };
throw myError;

然后，一旦在测试中发现错误，就可以测试错误的自定义内容。

expect(thrownError.data).toEqual({ name: 'myError',
                                   desc: 'myDescription' });

Answer 2

You need to throw a Javascript Error object, so the Jest toThrowError method identifies that an error has been thrown. Also the toThrowError looks to match the message of the error thrown or if an error has been thrown if you just check by .toThrowError().

it('should throw', () => {

  const errorObj = {
    myError: {
      name: 'myError',
      desc: 'myDescription'
    }
  };

  const fn = () => {
    throw new Error(errorObj.myError.desc);
  }

  expect(() => fn()).toThrowError("myDescription");
});

If you want to check the whole object is being passed as it is, you need to check it like this:

it('should throw', () => {

  const errorObj = {
    myError: {
      name: 'myError',
      desc: 'myDescription'
    }
  };

  const fn = () => {
    throw errorObj;
  }

  expect(() => fn()).toThrowError(new Error(errorObj));
});

Answer 3

这是笑话中的已知问题，请参阅https://github.com/facebook/jest/issues/8140

同时，这是我的解决方法 - https://github.com/DanielHreben/jest-matcher-specific-error