testing node.js class in module

Question

I'm writing a node.js module and my module has a private class.

I'm trying to write tests against this class, but can't figure out how to do that.

My module looks like this

var main = function(get_item){
   var main_item = new MyClass(get_item);
   return main_item
}

function MyClass(item){
  this.item = item;
  return this.init();
}

MyClass.prototype = {
   init: function(){
        return find_item();
    },
   find_item: function(){
     // does a bunch of stuff to look up an item
    },
    update_item: function(){
    // does a bunch of stuff to update the item
   },
  // a bunch more methods here
}

module.exports = main

// probably turn on and off for testing
module.exports = new MyClass //??? not sure how to do this

Then in my spec folder I've got

var main = require("./modules/myClass");

describe("get item",function(){
    it("should return an item",function(){
        var item_obj = main.get_item("first_item");
        expect(item_obj.index).toBe(1);
    })
});

I'm guessing their is a way for me to create a new class in my spec, but I'm not sure how, or how to export the class.

Answer 1

Using what you are currently doing, you would have to have

module.exports = { main: main, MyClass: MyClass }

Then use new mymodule.MyClass in your spec to instantiate your class. It would mean, though, that "regular" users of your class would have to do mymodule.main("Item") instead of mymodule("Item"), which changes the original interface of your module.

I have no idea if what I am about to suggest is a pattern or an anti-pattern, but here's one way to solve it:

module.exports = main;
module.exports.MyClass = MyClass; // only if testing

This was, your module's interface to regular users remains the same, and your spec can create an instance of the class by using new mymodule.MyClass().