[Containment] Disallow composition in immutable objects

Disallow composition in objects which cannot be created, under
the rationale that creatable objects must also be immutable.
WTD-1098.

platform/containment/test/CompositionMutabilityPolicySpec.js

@@ -0,0 +1,26 @@
+/*global define,Promise,describe,it,expect,beforeEach,waitsFor,jasmine*/
+
+define(
+    ["../src/CompositionMutabilityPolicy"],
+    function (CompositionMutabilityPolicy) {
+        "use strict";
+
+        describe("The composition mutability policy", function () {
+            var mockType,
+                policy;
+
+            beforeEach(function () {
+                mockType = jasmine.createSpyObj('type', ['hasFeature']);
+                policy = new CompositionMutabilityPolicy();
+            });
+
+            it("only allows composition for types which will have a composition capability", function () {
+                expect(policy.allow(mockType)).toBeFalsy();
+                mockType.hasFeature.andReturn(true);
+                expect(policy.allow(mockType)).toBeTruthy();
+                expect(mockType.hasFeature).toHaveBeenCalledWith('creation');
+            });
+        });
+
+    }
+);