Expect to throw force string equality instead of inclusion

[totty90]

expect(fn).to.throw(Error, "test")

will pass even if the error thrown in like this new Error('test2'). I would expect to don't pass as "test" is not equal to "test2".

In your docs you say:

string inclusion test for the error's message.

So it passes if the string is included. Is there any way to change the behaviour of this?

[keithamus]

@totty90 you can easily new up an error and achieve your desired result, something like this should work:

expect(fn).to.throw(new Error("test"));

Having said that - I do think our throw() assertion needs some work, see also #430. I'm going to devote some time to this soon, to try and change it for 3.0.0

[niftylettuce]

Same bug.

[niftylettuce]

See #551

[gurdiga]

@totty90 you can easily new up an error and achieve your desired result, something like this should work:

expect(fn).to.throw(new Error("test"));

It seems like this doesn’t work. =/

It looks like the expected and actual errors are compared strictly, and the result is that the assertion fails even if the error constructor and messages correspond. I have prepared a quick jsfiddle demo with chai v.3.4.1:

function throwingFunction() {
    throw new Error('A specific error message');
}

chai.expect(throwingFunction).to.throw(new Error('A specific error message'));

Check the browser console to find the assertion error message:

Uncaught AssertionError: expected [Function: throwingFunction] to throw 'Error: A specific error message' but 'Error: A specific error message' was thrown

I’m wondering if there I’m missing something. 8-|

[keithamus]

Hey @gurdiga - yes I was actually wrong above, passing two error instances will check for referential equality. 4.0.0 will change this (among other things). But we have a few outstanding PRs that I want to get merged in before I cut a release.

[gurdiga]

Sounds like a plan! Thank you! 8-)

[lucasfcosta]

Since we've got #683 merged, this has been solved.
Thanks everyone for your input 😄