feat(testability): add an initial scaffold for the testability api

Make each application component register itself onto the testability
API and exports the API onto the window object.

modules/angular2/test/core/application_spec.js

@@ -19,6 +19,7 @@ import {PromiseWrapper} from 'angular2/src/facade/async';
 import {bind, Inject} from 'angular2/di';
 import {Template} from 'angular2/src/core/annotations/template';
 import {LifeCycle} from 'angular2/src/core/life_cycle/life_cycle';
+import {Testability, TestabilityRegistry} from 'angular2/src/core/testability/testability';
 
 @Component({selector: 'hello-app'})
 @Template({inline: '{{greeting}} world!'})
@@ -180,5 +181,21 @@ export function main() {
         async.done();
       });
     }));
+
+    it('should register each application with the testability registry', inject([AsyncTestCompleter], (async) => {
+      var injectorPromise1 = bootstrap(HelloRootCmp, testBindings);
+      var injectorPromise2 = bootstrap(HelloRootCmp2, testBindings);
+
+      PromiseWrapper.all([injectorPromise1, injectorPromise2]).then((injectors) => {
+        var registry = injectors[0].get(TestabilityRegistry);
+        PromiseWrapper.all([
+            injectors[0].asyncGet(Testability),
+            injectors[1].asyncGet(Testability)]).then((testabilities) => {
+          expect(registry.findTestabilityInTree(el)).toEqual(testabilities[0]);
+          expect(registry.findTestabilityInTree(el2)).toEqual(testabilities[1]);
+          async.done();
+        });
+      });
+    }));
   });
 }

modules/angular2/test/core/testability/testability_spec.js

@@ -0,0 +1,42 @@
+import {describe, ddescribe, it, iit, xit, xdescribe, expect, beforeEach} from 'angular2/test_lib';
+import {Testability} from 'angular2/src/core/testability/testability';
+
+
+export function main() {
+  describe('Testability', () => {
+    var testability, executed;
+
+    beforeEach(() => {
+      testability = new Testability();
+      executed = false;
+    });
+
+    it('should start with a pending count of 0', () => {
+      expect(testability.getPendingCount()).toEqual(0);
+    });
+
+    it('should fire whenstable callbacks if pending count is 0', () => {
+      testability.whenStable(() => executed = true);
+      expect(executed).toBe(true);
+    });
+
+    it('should not call whenstable callbacks when there are pending counts', () => {
+      testability.increaseCount(2);
+      testability.whenStable(() => executed = true);
+
+      expect(executed).toBe(false);
+      testability.increaseCount(-1);
+      expect(executed).toBe(false);
+    });
+
+    it('should fire whenstable callbacks when pending drops to 0', () => {
+      testability.increaseCount(2);
+      testability.whenStable(() => executed = true);
+
+      expect(executed).toBe(false);
+
+      testability.increaseCount(-2);
+      expect(executed).toBe(true);
+    });
+  });
+}