new_contents: # pylint: disable=g-bad-file-header
  # Copyright 2019 The dm_env Authors. All Rights Reserved.
  #
  # 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.
  # ============================================================================
  """Tests for dm_env._environment."""
  
  from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  
  from absl.testing import absltest
  from absl.testing import parameterized
  import dm_env
  
  
  class TimeStepHelpersTest(parameterized.TestCase):
  
    @parameterized.parameters(dict(observation=-1), dict(observation=[2., 3.]))
    def test_restart(self, observation):
      time_step = dm_env.restart(observation)
      self.assertIs(dm_env.StepType.FIRST, time_step.step_type)
      self.assertEqual(observation, time_step.observation)
      self.assertEqual(None, time_step.reward)
      self.assertEqual(None, time_step.discount)
  
    @parameterized.parameters(
        dict(observation=-1., reward=2.0, discount=1.0),
        dict(observation=(2., 3.), reward=0., discount=0.))
    def test_transition(self, observation, reward, discount):
      time_step = dm_env.transition(
          reward=reward, observation=observation, discount=discount)
      self.assertIs(dm_env.StepType.MID, time_step.step_type)
      self.assertEqual(observation, time_step.observation)
      self.assertEqual(reward, time_step.reward)
      self.assertEqual(discount, time_step.discount)
  
    @parameterized.parameters(
        dict(observation=-1., reward=2.0),
        dict(observation=(2., 3.), reward=0.))
    def test_termination(self, observation, reward):
      time_step = dm_env.termination(reward=reward, observation=observation)
      self.assertIs(dm_env.StepType.LAST, time_step.step_type)
      self.assertEqual(observation, time_step.observation)
      self.assertEqual(reward, time_step.reward)
      self.assertEqual(0.0, time_step.discount)
  
    @parameterized.parameters(
        dict(observation=-1., reward=2.0, discount=1.0),
        dict(observation=(2., 3.), reward=0., discount=0.))
    def test_truncation(self, reward, observation, discount):
      time_step = dm_env.truncation(reward, observation, discount)
      self.assertIs(dm_env.StepType.LAST, time_step.step_type)
      self.assertEqual(observation, time_step.observation)
      self.assertEqual(reward, time_step.reward)
      self.assertEqual(discount, time_step.discount)
  
    @parameterized.parameters(
        dict(step_type=dm_env.StepType.FIRST,
             is_first=True, is_mid=False, is_last=False),
        dict(step_type=dm_env.StepType.MID,
             is_first=False, is_mid=True, is_last=False),
        dict(step_type=dm_env.StepType.LAST,
             is_first=False, is_mid=False, is_last=True),
    )
    def test_step_type_helpers(self, step_type, is_first, is_mid, is_last):
      time_step = dm_env.TimeStep(
          reward=None, discount=None, observation=None, step_type=step_type)
  
      with self.subTest('TimeStep methods'):
        self.assertEqual(is_first, time_step.first())
        self.assertEqual(is_mid, time_step.mid())
        self.assertEqual(is_last, time_step.last())
  
      with self.subTest('StepType methods'):
        self.assertEqual(is_first, time_step.step_type.first())
        self.assertEqual(is_mid, time_step.step_type.mid())
        self.assertEqual(is_last, time_step.step_type.last())
  
  
  if __name__ == '__main__':
    absltest.main()
  
subject: Add tests for `_environment` module.