[Fixed Position] Fill in specs for selection proxies

Fill in specs for fixed position views selection proxies,
WTD-879.

platform/features/layout/test/FixedProxySpec.js

@@ -6,7 +6,13 @@ define(
         "use strict";
 
         describe("Fixed Position view's selection proxy", function () {
-
+            it("has a placeholder message when clicked", function () {
+                var oldAlert = window.alert;
+                window.alert = jasmine.createSpy('alert');
+                new FixedProxy({}).add('');
+                expect(window.alert).toHaveBeenCalledWith(jasmine.any(String));
+                window.alert = oldAlert;
+            });
         });
     }
 );