Interface prototype contains defined methods

lib/interface.js

@@ -54,7 +54,12 @@ function extend()
         base      = args.pop() || Interface,
         prototype = new base();
 
-    var new_interface = {};
+    var new_interface = function() {};
+
+    util.propCopy( props, prototype );
+
+    new_interface.prototype   = prototype;
+    new_interface.constructor = new_interface;
 
     // freeze the interface (preventing additions), if supported
     util.freeze( new_interface );

test/test-interface-extend.js

@@ -59,3 +59,14 @@ assert.doesNotThrow(
     "Abstract method declarations are allowed within Interface definitions"
 );
 
+
+var BaseType = Interface.extend(
+{
+    method: abstractMethod(),
+});
+
+assert.ok(
+    ( BaseType.prototype.method instanceof Function ),
+    "Interface contains defined abstract methods"
+);
+

test/test-interface.js

@@ -32,8 +32,8 @@ var FooType = Interface.extend();
 
 
 assert.ok(
-    ( FooType instanceof Object ),
-    "Interface extend method creates a new object"
+    ( FooType instanceof Function ),
+    "Interface extend method creates a new interface object"
 );
 
 assert.equal(