Testing for exceptions

[Stefan Pöter]

Hi,

i've got a problem when testing for exceptions.

Maybe i missunderstood something here but shouldn't this example be a valid test?

var throwException = function() {

  throw {

    name: 'SomeException'

  }

}

expectThat(throwException(), throwsError());

gjstest prints out an error:

[object Object]

Thanks,

Stefan

[Aaron Jacobs]

Hi Stefan,

On Sun, Oct 9, 2011 at 12:13 AM, Stefan Pöter
<stefan...@googlemail.com> wrote:
> expectThat(throwException(), throwsError());

There are a couple of things wrong here: the subject of the expectation should
be a function, not a call to that function, and `throwsError` takes a regular
expression describing the error. So it should look like this:

expectThat(throwException, throwsError(/foo.*bar/));

This works correctly if the error thrown is instantiated from one of the
built-in types (for example by saying `new TypeError('foo bar')`). Since
`throwsError` looks at the string form of the error but your error object
doesn't have a helpful `toString` method, it won't work for your custom error,
however.

I've filed two issues to make the output more helpful when the user makes
these mistakes:

http://code.google.com/p/google-js-test/issues/detail?id=16
http://code.google.com/p/google-js-test/issues/detail?id=17

Aaron

[Stefan Pöter]

Hi Aaron,

thanks for your reply.

In that case i've written my own matcher looking like this:

throwsException = function(params, re) {

var description = 'is a function that throws an exception matching ' + re + ' with parameters' + params;

var negativeDescription = 'is a function that throws an exception not matching ' + re + ' with parameters ' + params;

var p = (typeof(params) === 'array' && params.length) ? params : [];

var r = (typeof(params) === 'string') ? params : re;

return new gjstest.Matcher(

description,

negativeDescription,

function(fnct) {

try {

fnct.apply(null, p);

expectTrue(false);

} catch(e) {

if (new RegExp(r).test(e.name)) {

return true;

}

return 'which threw wrong exception ' + e.name;

}

return 'which threw no exceptions';

}

);

};

Greetings

Stefan

[Stefan Pöter]

Ok, short explanation :-)

simply do

var fnct = function(a, b) {

  throw {

    name : 'SomeException'

  }

}

expectThat(fnct, throwsException([1, 2], 'SomeException'))

[Aaron Jacobs]

On Mon, Oct 10, 2011 at 6:21 PM, Stefan Pöter
<stefan...@googlemail.com> wrote:
> In that case i've written my own matcher looking like this:

Great! This may be the first public user-written matcher. :-)

Aaron