Real life testing with mocha ... how should I do it?

Let say I have "js" folder with the file "test.js" and only one function inside:

function isEven(number) {
    if (num%2 !== 0) return false;
    return true;
}

So, I write this code to test that JS file/code:

var chai = require('chai');
var expect = chai.expect;
var testObject = require('../js/test');

describe('Check isEven()', function() {

    it('Should return boolean', function() {

        var result = isEven(77);

        expect(result).to.be.a('boolean');

    });

});

But this produces "undefined is not a function". So, how am I supposed to access code from included file in this case?

PS: I've seen similar stuff, done with Require.js, but what if my app doesn't use Require.js at all?