Fix observable transform bug introduced in a recent change, add regression tests

pkg/observe/test/transform_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:async';
 import 'package:barback/barback.dart';
 import 'package:observe/transform.dart';
 import 'package:unittest/compact_vm_config.dart';
 import 'package:unittest/unittest.dart';
 
@@ skipping 28 matching lines @@
   group('fixes contructor calls ', () {
     _testInitializers('this.a', '(a) : __\$a = a');
     _testInitializers('{this.a}', '({a}) : __\$a = a');
     _testInitializers('[this.a]', '([a]) : __\$a = a');
     _testInitializers('this.a, this.b', '(a, b) : __\$a = a, __\$b = b');
     _testInitializers('{this.a, this.b}', '({a, b}) : __\$a = a, __\$b = b');
     _testInitializers('[this.a, this.b]', '([a, b]) : __\$a = a, __\$b = b');
     _testInitializers('this.a, [this.b]', '(a, [b]) : __\$a = a, __\$b = b');
     _testInitializers('this.a, {this.b}', '(a, {b}) : __\$a = a, __\$b = b');
   });
+
+  group('test full text', () {
+    test('with changes', () {
+      return _transform(_sampleObservable('A', 'foo'))
+        .then((output) => expect(output, _sampleObservableOutput('A', 'foo')));
+    });
+
+    test('no changes', () {
+      var input = 'class A {/*@observable annotation to trigger transform */;}';
+      return _transform(input).then((output) => expect(output, input));
+    });
+  });
 }
 
 _testClause(String clauses, String expected) {
   test(clauses, () {
     var className = 'MyClass';
     if (clauses.contains('<T>')) className += '<T>';
     var code = '''
       class $className $clauses {
         @observable var field;
       }''';
@@ skipping 52 matching lines @@
   _MockTransform(this._asset);
   Future<Asset> getInput(Asset id) {
     if (id == primaryInput.id) return new Future.value(primaryInput);
     fail();
   }
 
   void addOutput(Asset output) {
     outs.add(output);
   }
 }
+
+String _sampleObservable(String className, String fieldName) => '''
+library ${className}_$fieldName;
+import 'package:observe/observe.dart';
+
+class $className extends ObservableBase {
+  @observable int $fieldName;
+  $className(this.$fieldName);
+}
+''';
+
+String _sampleObservableOutput(String className, String fieldName) => '''
+library ${className}_$fieldName;
+import 'package:observe/observe.dart';
+
+class $className extends ChangeNotifierBase {
+  int __\$$fieldName;
+  int get $fieldName => __\$$fieldName;
+  set $fieldName(int value) {
+    __\$$fieldName = notifyPropertyChange(const Symbol('$fieldName'), __\$$fieldName, value);
+  }
+  
+  $className($fieldName) : __\$$fieldName = $fieldName;
+}
+''';