feat(test): add angular2_testing dart library

angular2_testing is a user-facing dart test library built on top of
the package:test dart unittest framework and runner. For usage,
see modules_dart/angular2_testing/README.md.

Closes #3289

modules_dart/angular2_testing/test/angular2_testing_test.dart

@@ -0,0 +1,99 @@
+// Because Angular is using dart:html, we need these tests to run on an actual
+// browser. This means that it should be run with `-p dartium` or `-p chrome`.
+@TestOn('browser')
+import 'package:angular2/angular2.dart'
+    show Component, View, NgFor, provide, Inject, Injectable, Optional;
+
+import 'package:test/test.dart';
+import 'package:angular2_testing/angular2_testing.dart';
+
+// This is the component we will be testing.
+@Component(selector: 'test-cmp')
+@View(directives: const [NgFor])
+class TestComponent {
+  List<num> items;
+  TestComponent() {
+    this.items = [1, 2];
+  }
+}
+
+@Injectable()
+class TestService {
+  String status = 'not ready';
+
+  init() {
+    this.status = 'ready';
+  }
+}
+
+class MyToken {}
+
+const TEMPLATE =
+    '<div><copy-me template=\'ng-for #item of items\'>{{item.toString()}};</copy-me></div>';
+
+void main() {
+  initAngularTests();
+
+  setUpProviders(() => [provide(MyToken, useValue: 'my string'), TestService]);
+
+  test('normal function', () {
+    var string = 'foo,bar,baz';
+    expect(string.split(','), equals(['foo', 'bar', 'baz']));
+  });
+
+  ngTest('can grab injected values', (@Inject(MyToken) token, TestService testService) {
+    expect(token, equals('my string'));
+    expect(testService.status, equals('not ready'));
+  });
+
+  group('nested ngSetUp', () {
+    ngSetUp((TestService testService) {
+      testService.init();
+    });
+
+    ngTest('ngSetUp modifies injected services', (TestService testService) {
+      expect(testService.status, equals('ready'));
+    });
+  });
+
+  ngTest('create a component using the TestComponentBuilder', (TestComponentBuilder tcb) async {
+    var rootTC = await tcb
+        .overrideTemplate(TestComponent, TEMPLATE)
+        .createAsync(TestComponent);
+
+    rootTC.detectChanges();
+    expect(rootTC.debugElement.nativeElement.text, equals('1;2;'));
+  });
+
+  ngTest('should reflect added elements', (TestComponentBuilder tcb) async {
+    var rootTC = await tcb
+        .overrideTemplate(TestComponent, TEMPLATE)
+        .createAsync(TestComponent);
+
+    rootTC.detectChanges();
+    (rootTC.debugElement.componentInstance.items as List<num>).add(3);
+    rootTC.detectChanges();
+
+    expect(rootTC.debugElement.nativeElement.text, equals('1;2;3;'));
+  });
+
+  group('expected failures', () {
+    ngTest('no type in param list', (notTyped) {
+      expect(1, equals(2));
+    });
+
+    ngSetUp((TestService testService) {
+      testService.init();
+    });
+
+    // This would fail, since setUpProviders is used after a call to ngSetUp has already
+    // initialized the injector.
+    group('nested', () {
+      setUpProviders(() => [TestService]);
+
+      test('foo', () {
+        expect(1 + 1, equals(2));
+      });
+    });
+  }, skip: 'expected failures');
+}