fix(introspection): getTestability should throw when ElementProbes are unavailable

Author: chirayuk

lib/introspection.dart

@@ -209,6 +209,9 @@ _jsify(var obj) {
   if (obj == null || obj is js.JsObject) {
     return obj;
   }
+  if (obj is _JsObjectProxyable) {
+    return obj._toJsObject();
+  }
   if (obj is Function) {
     return _jsFunction(obj);
   }
@@ -269,7 +272,6 @@ class _Testability implements _JsObjectProxyable {
   final ElementProbe probe;
 
   _Testability(this.node, this.probe);
-  _Testability.fromNode(dom.Node node): this(node, _findProbeInTree(node));
 
   notifyWhenNoOutstandingRequests(callback) {
     probe.injector.get(VmTurnZone).run(
@@ -336,6 +338,18 @@ class _Testability implements _JsObjectProxyable {
 }
 
 
+_Testability getTestability(dom.Node node) {
+  ElementProbe probe = _findProbeInTree(node);
+  if (probe == null) {
+    throw ("Could not find an ElementProbe for $node.  This might happen "
+           "either because there is no Angular directive for that node OR "
+           "because your application is running with ElementProbes disabled "
+           "(CompilerConfig.elementProbeEnabled = false).");
+  }
+  return new _Testability(node, probe);
+}
+
+
 void publishToJavaScript() {
   var D = {};
   D['ngProbe'] = (nodeOrSelector) => _jsProbe(ngProbe(nodeOrSelector));
@@ -345,7 +359,7 @@ void publishToJavaScript() {
       ngQuery(node, selector, containsText);
   D['angular'] = {
         'resumeBootstrap': ([arg]) {},
-        'getTestability': (node) => new _Testability.fromNode(node)._toJsObject(),
+        'getTestability': getTestability,
   };
   js.JsObject J = _jsify(D);
   for (String key in D.keys) {

test/angular_spec.dart

@@ -227,6 +227,7 @@ main() {
         "angular.formatter_internal.OrderBy",
         "angular.formatter_internal.Stringify",
         "angular.formatter_internal.Uppercase",
+        "angular.introspection.getTestability",
         "angular.introspection.ngDirectives",
         "angular.introspection.ngInjector",
         "angular.introspection.ngProbe",

test/introspection_spec.dart

@@ -53,6 +53,42 @@ void main() {
       expect(toHtml(ngQuery(div, 'li'))).toEqual('<li>stash</li><li>secret</li>');
     });
 
+    describe('getTestability', () {
+      for (bool elementProbeEnabled in [false, true]) {
+        describe('elementProbeEnabled=$elementProbeEnabled', () {
+          var elt;
+
+          beforeEachModule((Module m) {
+            m.bind(CompilerConfig, toValue:
+                new CompilerConfig.withOptions(elementProbeEnabled: elementProbeEnabled));
+          });
+
+          beforeEach((TestBed _) {
+            elt = _.compile('<div ng-bind="0"></div>');
+            document.body.append(elt);
+          });
+
+          afterEach(() {
+            elt.remove();
+          });
+
+          if (elementProbeEnabled) {
+            it('should return a Testability object', () {
+              expect(getTestability(elt)).toBeDefined();
+            });
+          } else {
+            it('should throw an exception', () {
+              expect(() => getTestability(elt)).toThrow(
+                  "Could not find an ElementProbe for div.  This might happen "
+                  "either because there is no Angular directive for that node OR "
+                  "because your application is running with ElementProbes "
+                  "disabled (CompilerConfig.elementProbeEnabled = false).");
+            });
+          }
+        });
+      }
+    });
+
     describe('JavaScript bindings', () {
       var elt, angular, ngtop;
 
@@ -92,6 +128,7 @@ void main() {
       // Issue #1219
       if (identical(1, 1.0) || !js.context['DART_VERSION'].toString().contains("version: 1.5.")) {
         describe(r'testability', () {
+
           var testability;
 
           beforeEach(() {