Prevent you from registering multiple classes with the same Id

lib/container.js

@@ -58,6 +58,10 @@ class Container {
       throw CannotRegisterClassError(clazz, type);
     }
 
+    if (this.types[type][id]) {
+      throw ClassAlreadyRegisteredWithId(clazz, type);
+    }
+
     clazz.id = id;
     clazz.type = type;
 
@@ -156,4 +160,14 @@ function CannotRegisterClassError(clazz, type) {
   }
 
   return new Error(message + type + ' because it does not have an Id.');
+}
+
+function ClassAlreadyRegisteredWithId(clazz, type) {
+  var message = 'Cannot register ';
+
+  if (clazz && clazz.displayName) {
+    message += clazz.displayName + ' ';
+  }
+
+  return new Error(message + type + ' because there is already a class with that Id.');
 }

test/browser/containerSpec.js

@@ -28,6 +28,24 @@ describe('Container', function () {
     sandbox.restore();
   });
 
+  describe('when there are two classes with the same Id', function () {
+    var Store1, Store2;
+
+    beforeEach(function () {
+      expectedId = 'Foo';
+
+      Marty.createStore({ id: expectedId });
+    });
+
+    it('should throw an error when you try to register the second class', function () {
+      expect(registerSecondClass).to.throw(Error);
+
+      function registerSecondClass() {
+        Marty.createStore({ id: expectedId });
+      }
+    });
+  })
+
   describe('stores', function () {
     var expectedStore, expectedFoo, actualStore, actionCreators, defaultStore;
 

test/browser/stateMixinSpec.js

@@ -421,7 +421,7 @@ describe('StateMixin', function () {
 
   function createStore(state) {
     return Marty.createStore({
-      id: 'stateMixin',
+      id: uuid.type('StateMixin'),
       getInitialState: function () {
         return state || {};
       }