如前所述，需要将函数传递给toThrow，因为它是您在测试中描述的函数:“I expect this function to throw x”

expect(() => parser.parse(raw))
  .toThrow(new Error('Parsing is not possible'));

如果使用茉莉花-匹配器，你也可以使用以下其中之一，当他们适合的情况;

// I just want to know that an error was
// thrown and nothing more about it
expect(() => parser.parse(raw))
  .toThrowAnyError();

or

// I just want to know that an error of 
// a given type was thrown and nothing more
expect(() => parser.parse(raw))
  .toThrowErrorOfType(TypeError);

在我的例子中，抛出错误的函数是异步的，所以我遵循了这一点:

await expectAsync(asyncFunction()).toBeRejected();
await expectAsync(asyncFunction()).toBeRejectedWithError(...);

it('it should fail', async () => {
    expect.assertions(1);

    try {
        await testInstance.doSomething();
    }
    catch (ex) {
        expect(ex).toBeInstanceOf(MyCustomError);
    }
});

您正在使用:

expect(fn).toThrow(e)

但是如果你看一下函数注释(expected is string):

294 /**
295  * Matcher that checks that the expected exception was thrown by the actual.
296  *
297  * @param {String} expected
298  */
299 jasmine.Matchers.prototype.toThrow = function(expected) {

我想你应该这样写(使用lambda - anonymous函数):

expect(function() { parser.parse(raw); } ).toThrow("Parsing is not possible");

下面的例子证实了这一点:

expect(function () {throw new Error("Parsing is not possible")}).toThrow("Parsing is not possible");

Douglas Crockford强烈推荐这种方法，而不是使用“throw new Error()”(原型):

throw {
   name: "Error",
   message: "Parsing is not possible"
}

尝试使用匿名函数:

expect( function(){ parser.parse(raw); } ).toThrow(new Error("Parsing is not possible"));

您应该向expect(…)调用传递一个函数。你的错误代码:

// incorrect:
expect(parser.parse(raw)).toThrow(new Error("Parsing is not possible"));

实际上是试图调用parser.parse(raw)，试图将结果传递给expect(…)，

我用下面的代码替换了Jasmine的toThrow匹配器，它允许您匹配异常的name属性或其message属性。对我来说，这使得测试更容易编写，也不那么脆弱，因为我可以做到以下几点:

throw {
   name: "NoActionProvided",
   message: "Please specify an 'action' property when configuring the action map."
}

然后用下面的方法进行测试:

expect (function () {
   .. do something
}).toThrow ("NoActionProvided");

这让我可以稍后在不中断测试的情况下调整异常消息，而重要的是它抛出了预期的异常类型。

这是toThrow的替代物，允许这样做:

jasmine.Matchers.prototype.toThrow = function(expected) {
  var result = false;
  var exception;
  if (typeof this.actual != 'function') {
    throw new Error('Actual is not a function');
  }
  try {
    this.actual();
  } catch (e) {
    exception = e;
  }
  if (exception) {
      result = (expected === jasmine.undefined || this.env.equals_(exception.message || exception, expected.message || expected) || this.env.equals_(exception.name, expected));
  }

  var not = this.isNot ? "not " : "";

  this.message = function() {
    if (exception && (expected === jasmine.undefined || !this.env.equals_(exception.message || exception, expected.message || expected))) {
      return ["Expected function " + not + "to throw", expected ? expected.name || expected.message || expected : " an exception", ", but it threw", exception.name || exception.message || exception].join(' ');
    } else {
      return "Expected function to throw an exception.";
    }
  };

  return result;
};