[Fixed Position] Fill in specs for selection proxies

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

platform/features/layout/test/elements/ElementProxiesSpec.js

@@ -5,8 +5,23 @@ define(
     function (ElementProxies) {
         "use strict";
 
-        describe("The set of element proxies", function () {
+        var ELEMENT_TYPES = [
+            "fixed.telemetry"
+        ];
 
+        // Verify that the set of proxies exposed matches the specific
+        // list above.
+        describe("The set of element proxies", function () {
+            ELEMENT_TYPES.forEach(function (t) {
+                it("exposes a proxy wrapper for " + t + " elements", function () {
+                    expect(typeof ElementProxies[t]).toEqual('function');
+                });
+            });
+
+            it("exposes no additional wrappers", function () {
+                expect(Object.keys(ElementProxies).length)
+                    .toEqual(ELEMENT_TYPES.length);
+            });
         });
     }
 );