text: # Copyright 2019, OpenCensus Authors
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #     http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  try:
      from mock import Mock
  except ImportError:
      from unittest.mock import Mock
  
  import unittest
  
  from opencensus.metrics.export import metric_producer
  
  
  class TestMetricProducerManager(unittest.TestCase):
      def test_init(self):
          mpm1 = metric_producer.MetricProducerManager()
          self.assertEqual(mpm1.metric_producers, set())
  
          mock_mp = Mock()
          mpm2 = metric_producer.MetricProducerManager([mock_mp])
          self.assertEqual(mpm2.metric_producers, set([mock_mp]))
  
      def test_add_remove(self):
          mpm = metric_producer.MetricProducerManager()
          self.assertEqual(mpm.metric_producers, set())
  
          with self.assertRaises(ValueError):
              mpm.add(None)
          mock_mp = Mock()
          mpm.add(mock_mp)
          self.assertEqual(mpm.metric_producers, set([mock_mp]))
          mpm.add(mock_mp)
          self.assertEqual(mpm.metric_producers, set([mock_mp]))
  
          with self.assertRaises(ValueError):
              mpm.remove(None)
          another_mock_mp = Mock()
          mpm.remove(another_mock_mp)
          self.assertEqual(mpm.metric_producers, set([mock_mp]))
          mpm.remove(mock_mp)
          self.assertEqual(mpm.metric_producers, set())
  
      def test_get_all(self):
          mp1 = Mock()
          mp2 = Mock()
          mpm = metric_producer.MetricProducerManager([mp1, mp2])
          got = mpm.get_all()
          mpm.remove(mp1)
          self.assertIn(mp1, got)
          self.assertIn(mp2, got)
  