Add string support to throws

[SamVerschueren]

I added the possibility to pass in the error message as string to the throws method.

Example

test('test it', t => {
    t.throws(throws, 'foo bar');
    t.end();

    function throws() {
        throw new Error('foo bar');
    }
});

Benefit

If you want to test the returned error message you either should use a regex or a validation function. The validation function spoils the test file in my opinion, and the regex is, well yeah, it's a regex. People have to escape some characters and a string just looks cleaner.

Downside

Not sure if it is a downside, but it's not standard assert stuff which might confuse people. Although, I don't really see it as downside, it's more an improvement.

// @sindresorhus @vdemedes @kevva @Qix-

[Qix-]

should does this and to be honest it's the only way I could see reliably testing for expected exceptions. Expecting an exception but not specifying which one introduced a few regressions before I realized I needed to specify the message.

[sindresorhus]

Not sure if it is a downside, but it's not standard assert stuff which might confuse people.

It's not. We only use the core assert so not to duplicate code. If anything can be done better, we'll do it. Also the core Node.js people have said assert is done and won't change anymore.

👍 from me.

[Qix-]

Also the core Node.js people have said assert is done and won't change anymore.

One of my problems with the Node team. /offtopic

[SamVerschueren]

Things can always be done better!

[sindresorhus]

@Qix- In their defense it was a mistake to expose it as it was only really meant to be used to test core, from what I've read.

Also why ideally almost everything should be in user-land so it can be individually versioned and evolved.

[Qix-]

That makes sense.

[sindresorhus]

if (typeof err === 'string') {
  err = function (e) {
    return e.message === err;
  };
}

assert.throws(fn, err, msg);

[SamVerschueren]

Definitely cleaner, but then I guess it should be like this.

if (typeof err === 'string') {
  var e = err;
  err = function (err) {
    return err.message === e;
  };
}

assert.throws(fn, err, msg);

In your example, at the time the function is executed, err is not the string anymore but it is the function. So it will check if err.message is equal to the function instead of to the original string.

[sindresorhus]

Yup

[sindresorhus]

👍 Thanks Sam :)

[SamVerschueren]

No problem, always happy to contribute ;).

Any idea when these latest changes (string support in throws, promise fix in throws) will be released? They are needed in pageres and gh-user :). (and many others off course)

[sindresorhus]

@SamVerschueren Hopefully today. Just want to get in the two open PRs. Any help reviewing #120 welcome ;)

[SamVerschueren]

That's not an easy one :). Will have a look at it later today.