Add util to verify constructor calls use 'new'

lib/adaptor.js

@@ -24,6 +24,8 @@ function formatErrorMessage(name, message) {
 //
 // Returns a new Adaptor
 var Adaptor = module.exports = function Adaptor(opts) {
+  Adaptor.__super__.constructor.apply(this, arguments);
+
   opts = opts || {};
 
   this.name = opts.name;

lib/basestar.js

@@ -19,6 +19,7 @@ var Utils = require("./utils"),
 // It also extends EventEmitter, so child classes are capable of emitting events
 // for other parts of the system to handle.
 var Basestar = module.exports = function Basestar() {
+  Utils.classCallCheck(this, Basestar);
 };
 
 Utils.subclass(Basestar, EventEmitter);

lib/driver.js

@@ -24,6 +24,8 @@ function formatErrorMessage(name, message) {
 //
 // Returns a new Driver
 var Driver = module.exports = function Driver(opts) {
+  Driver.__super__.constructor.apply(this, arguments);
+
   opts = opts || {};
 
   this.name = opts.name;

lib/robot.js

@@ -27,6 +27,8 @@ var Async = require("async"),
 //
 // Returns a new Robot
 var Robot = module.exports = function Robot(opts) {
+  Utils.classCallCheck(this, Robot);
+
   opts = opts || {};
 
   var methods = [

lib/utils.js

@@ -145,6 +145,12 @@ var Utils = module.exports = {
     return base;
   },
 
+  classCallCheck: function(instance, Constructor) {
+    if (!(instance instanceof Constructor)) {
+      throw new TypeError("Cannot call a class as a function");
+    }
+  },
+
   // Public: Analogue to Ruby"s Hash#fetch method for looking up object
   // properties.
   //

spec/lib/utils.spec.js

@@ -251,4 +251,22 @@ describe("Utils", function() {
       });
     });
   });
+
+  describe("#classCallCheck", function() {
+    it("checks that an object is an instance of a constructor", function() {
+      var fn = function(instance, Constructor) {
+        return utils.classCallCheck.bind(null, instance, Constructor);
+      };
+
+      function Class() {
+        utils.classCallCheck(this, Class);
+      }
+
+      expect(fn([], Array)).to.not.throw;
+      expect(fn([], Number)).to.throw(TypeError);
+
+      expect(Class).to.throw(TypeError);
+      expect(function() { return new Class(); }).not.to.throw(TypeError);
+    });
+  });
 });