Fix and unit test for batch_watch context manager

param/__init__.py

@@ -28,7 +28,7 @@
 from .parameterized import Parameterized, Parameter, String, \
      descendents, ParameterizedFunction, ParamOverrides
 from .parameterized import (depends, output, logging_level, # noqa: api import
-     shared_parameters, instance_descriptor)
+    shared_parameters, instance_descriptor, batch_watch)
 
 from collections import OrderedDict
 from numbers import Real

param/parameterized.py

@@ -88,7 +88,7 @@ def batch_watch(parameterized, run=True):
     finally:
         parameterized.param._BATCH_WATCH = BATCH_WATCH
         if run and not BATCH_WATCH:
-            obj.param._batch_call_watchers()
+            parameterized.param._batch_call_watchers()
 
 
 def classlist(class_):

tests/API1/testwatch.py

@@ -202,6 +202,29 @@ def test_simple_batched_watch_setattr(self):
         self.assertEqual(args[0].new, 3)
         self.assertEqual(args[0].type, 'changed')
 
+    def test_batched_watch_context_manager(self):
+
+        accumulator = Accumulator()
+
+        obj = SimpleWatchExample()
+        obj.param.watch(accumulator, ['a','b'])
+
+        with param.batch_watch(obj):
+            obj.a = 2
+            obj.b = 3
+
+        self.assertEqual(accumulator.call_count(), 1)
+        args = accumulator.args_for_call(0)
+
+        self.assertEqual(len(args), 2)
+        self.assertEqual(args[0].name, 'a')
+        self.assertEqual(args[0].old, 0)
+        self.assertEqual(args[0].new, 2)
+        self.assertEqual(args[0].type, 'changed')
+        self.assertEqual(args[1].name, 'b')
+        self.assertEqual(args[1].old, 0)
+        self.assertEqual(args[1].new, 3)
+        self.assertEqual(args[1].type, 'changed')
 
     def test_nested_batched_watch_setattr(self):