https://github.com/visionmedia/mocha/blob/master/lib/hook.js
It boils down to something like this:
"use strict";
function MyClass(arg1) {
this.instanceVariable = arg1;
// stuff
}
function privateFunction() {
// stuff
}
MyClass.prototype._privateMethod = function () {
//stuff
};
MyClass.prototype.publicMethod = function () {
//stuff
};
module.exports = MyClass;