Mocha assert.throws - I have no idea how to make it work

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#1

For Mocha Rooster Regulation project. I’ve tried looking at the documentation and another tutorial, but assert.throws is a weird one and I have no idea what it wants in order to work, and I’ve tried a couple things.

const assert = require('assert');
const Rooster = require('../index');

describe('Rooster', () => {
  describe('.timeAtDawn', () => {
    it('throws an error if passed a number less than 0', () => {
      // Define expected output
      const err = new RangeError;
      assert.throws(() => {
        Rooster.timeAtDawn(-1);
      }, err);
    });
  });
});

If it was coded correctly, it would pass. Instead I get the following output:

1) Rooster .timeAtDawn throws an error if passed a number less than 0:
     TypeError: expected.call is not a function
      at expectedException (assert.js:314:19)
      at _throws (assert.js:360:8)
      at Function.throws (assert.js:369:3)
      at Context.it (test/index_test.js:33:14) // this is the line with assert.throws

npm ERR! Test failed.  See above for more details.

I’ve tried other things that failed too.

#2

I went back to mine and I didn’t have the new keyword, but I get the same issue as you if I add it in. I’m pretty sure I ran into this same issue when I went through the lesson and had to change it.

My understanding is that assert.throws() is expecting a Class, but not an instance of the Class. It also accepts other types as well, of course.

#3

Removing new fixed it. Made sure the test passes and fails when it should, and everything is working now. I really appreciate the help.

This is definitely something I need to read up on more.