Node assert.throws not catching exception

Question

Given this code:

var assert = require(\'assert\');

function boom(){
    throw new Error(\'BOOM\');
}

assert.throws( boom(), Error );

I ge

Answer 1

Current node stable (v4.1) includes fat arrow function support by default (no --harmony flag required) so you can do something like:

assert.throws(()=>boom(), Error);
assert.throws(()=>boom(true), Error); // with params

Even if you have parentheses after boom() (so you're actually invoking it, instead of passing a reference to the function object), by using the fat arrow function you're wrapping it in a block, which is what assert.throws expects.

Answer 2

You can use bind():

assert.throws( boom.bind(null), Error );

With arguments it is:

assert.throws( boom.bind(null, "This is a blowup"), Error );

Answer 3

This is closely related to the issue people with with other assertion Mocha/Chai. See this answer for the description with node examples:
Mocha / Chai expect.to.throw not catching thrown errors

Answer 4

The examples take a function, while your sample code calls a function and passes the result. The exception happens before the assert even gets to look at it.

Change your code to this:

var assert = require('assert');

function boom(){
    throw new Error('BOOM');
}

assert.throws( boom, Error ); // note no parentheses

EDIT: To pass parameters, just make another function. After all, this is javascript!

var assert = require('assert');

function boom(blowup){
    if(blowup)
        throw new Error('BOOM');
}

assert.throws( function() { boom(true); }, Error );