def testOneofMessageMergeFrom(self, message_module):
    m = message_module.NestedTestAllTypes()
    m.payload.oneof_nested_message.bb = 11
    m.child.payload.oneof_nested_message.bb = 12
    m2 = message_module.NestedTestAllTypes()
    m2.payload.oneof_uint32 = 13
    m2.MergeFrom(m)
    self.assertEqual('oneof_nested_message',
                     m2.payload.WhichOneof('oneof_field'))
    self.assertEqual('oneof_nested_message',
                     m2.child.payload.WhichOneof('oneof_field'))