package:observe fix various api issues

pkg/observe/test/observe_test_utils.dart

Index: pkg/observe/test/observe_test_utils.dart
diff --git a/pkg/observe/test/observe_test_utils.dart b/pkg/observe/test/observe_test_utils.dart
index 2937c07a851f5effee9c80c196a4c3bf94bc49c3..2025e1b87addf546708cd4727d9ecfcb050064da 100644
--- a/pkg/observe/test/observe_test_utils.dart
+++ b/pkg/observe/test/observe_test_utils.dart
@@ -4,6 +4,8 @@
 
 library observe.test.observe_test_utils;
 
+import 'package:observe/observe.dart';
+
 import 'package:unittest/unittest.dart';
 
 import 'package:observe/src/microtask.dart';
@@ -14,6 +16,12 @@ export 'package:observe/src/microtask.dart';
 expectChanges(actual, expected, {reason}) =>
     expect('$actual', '$expected', reason: reason);
 
+List getListChangeRecords(List changes, int index) => changes
+    .where((c) => c is ListChangeRecord && c.indexChanged(index)).toList();
+
+List getPropertyChangeRecords(List changes, Symbol property) => changes
+    .where((c) => c is PropertyChangeRecord && c.name == property).toList();
+
 /**
  * This is a special kind of unit [test], that supports
  * calling [performMicrotaskCheckpoint] during the test to pump events