Using Mock Objects with Node.js and Jasmine

user-authenticator.js

var events = require("events"),
    util = require("util");

var UserAuthenticator = function(user_finder){
    this.user_finder = user_finder;
};
util.inherits(UserAuthenticator, events.EventEmitter);

UserAuthenticator.make = function(dependencies){
    var authenticator = new UserAuthenticator(dependencies.user_finder);
    return authenticator;
};
UserAuthenticator.create = function(){};
UserAuthenticator.prototype.authenticate = function(email, password){
    var self = this;
    this.user_finder.on("user-found", function(user){
	if (user.password == password) {
	    self.emit("authenticated");
	} else {
	    self.emit("invalid-password");
	}
    });

    this.user_finder.on("user-not-found", function(){
	self.emit("user-not-found");
    });

    this.user_finder.find_by_email(email);
};


module.exports = UserAuthenticator;

user-authenticator.spec.js

var util = require("util"),
    events = require("events");

var mock = {};
mock.UserFinder = (function(){
    var klass = function(){};
    util.inherits(klass, events.EventEmitter);

    klass.prototype.find_by_email = function(email){};

    return klass;
})();

var UserAuthenticator = require("./user-authenticator");

describe("UserAuthenticator", function(){
    beforeEach(function(){
	this.valid_user = {
	    email:"foo@example.com",
	    password:"bar"
	};

        this.user_finder = new mock.UserFinder();

        this.authenticator = UserAuthenticator.make({
            user_finder: this.user_finder
        });
    });

    it("looks up the user by email", function(){
	spyOn(this.user_finder, "find_by_email");
	var email = "foo@example.com";

	this.authenticator.authenticate(email, null);
	expect(this.user_finder.find_by_email).toHaveBeenCalledWith(email);
    });

    it("emits an 'authenticated' event when valid credentials are passed", function(){
	spyOn(this.authenticator,'emit');
	this.authenticator.authenticate(this.valid_user.email, this.valid_user.password);
	this.user_finder.emit("user-found",this.valid_user);
	expect(this.authenticator.emit).toHaveBeenCalledWith("authenticated");
    });

    it("emits an 'user-not-found' event when an unknown email address is passed", function(){	
	spyOn(this.authenticator,'emit');
	this.authenticator.authenticate(null, null);
	this.user_finder.emit("user-not-found");
	expect(this.authenticator.emit).toHaveBeenCalledWith("user-not-found");
    });

    it("emits an 'invalid-password' event when a the passed email and password do not match", function(){
	spyOn(this.authenticator,'emit');
	this.authenticator.authenticate(this.valid_user, null);
	this.user_finder.emit("user-found", this.valid_user);
	expect(this.authenticator.emit).toHaveBeenCalledWith("invalid-password");
    });
});

user-finder.js

/**
 * Example implementation of UserFinder. It depends on a UserRepository object. 
 */

var util = require("util"),
    events = require("events");

var UserFinder = function(user_repository){
    this.user_repository = user_repository;
};
UserFinder.make = function(dependencies){
    return new UserFinder(dependencies.user_repository);
};
UserFinder.create = function(){
    var users = new UserRepository();
    return UserFinder.make({
	user_repository: users
    });
};

util.inherits(UserFinder, events.EventEmitter);

// This should be tested with an integration test (ie. it should hit a real database)
UserFinder.prototype.find_by_email = function(email){
    var self = this;
    this.repository.get({email: email}, function(user){
	if (user) {
	    self.emit("user-found", user);
	} else {
	    self.emit("user-not-found");
	}
    });
};