feat(core): introduce @AppModule

Main part for #9726
Closes #9730

modules/@angular/core/test/di/injector_spec.ts

@@ -0,0 +1,27 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+
+import {Injector} from '@angular/core';
+import {beforeEach, ddescribe, describe, expect, iit, it} from '@angular/core/testing/testing_internal';
+
+import {IS_DART} from '../../src/facade/lang';
+
+export function main() {
+  describe('Injector.NULL', () => {
+    it('should throw if no arg is given', () => {expect(() => Injector.NULL.get('someToken'))
+                                                     .toThrowError('No provider for someToken!')});
+
+    it('should throw if THROW_IF_NOT_FOUND is given',
+       () => {expect(() => Injector.NULL.get('someToken', Injector.THROW_IF_NOT_FOUND))
+                  .toThrowError('No provider for someToken!')});
+
+    it('should return the default value',
+       () => { expect(Injector.NULL.get('someToken', 'notFound')).toEqual('notFound'); });
+  });
+}