Update tests to support pytest 5.x

Our tests were using pytest fixtures by actually calling the fixture
methods, but in newer 5.x versions of pytest this causes test failures.
The recommended method for using fixtures is dependency injection.

This change updates the relevant test fixtures to either not use
`pytest.fixture` or to use dependency injection to pass the fixture.
The version range requirements in `test_requirements.txt` were also
updated accordingly.

ml-agents/mlagents/trainers/tests/test_learn.py

 from mlagents.trainers.learn import parse_command_line
 
 
-@pytest.fixture
 def basic_options(extra_args=None):
     extra_args = extra_args or {}
     args = ["basic_path"]

ml-agents/mlagents/trainers/tests/test_rl_trainer.py

 from mlagents.trainers.buffer import AgentBuffer
 
 
-@pytest.fixture
 def dummy_config():
     return yaml.safe_load(
         """

ml-agents/mlagents/trainers/tests/test_sac.py

             sess.run(run_list, feed_dict=feed_dict)
 
 
-def test_sac_save_load_buffer(tmpdir):
+def test_sac_save_load_buffer(tmpdir, dummy_config):
     env, mock_brain, _ = mb.setup_mock_env_and_brains(
         mock.Mock(),
         False,
         vector_obs_space=VECTOR_OBS_SPACE,
         discrete_action_space=DISCRETE_ACTION_SPACE,
     )
-    trainer_params = dummy_config()
+    trainer_params = dummy_config
     trainer_params["summary_path"] = str(tmpdir)
     trainer_params["model_path"] = str(tmpdir)
     trainer_params["save_replay_buffer"] = True

ml-agents/mlagents/trainers/tests/test_trainer_controller.py

 from unittest.mock import MagicMock, Mock, patch
+import pytest
-
-import yaml
-import pytest
-
 from mlagents.trainers.trainer_controller import TrainerController
 from mlagents.trainers.subprocess_env_manager import EnvironmentStep
 from mlagents.trainers.sampler_class import SamplerManager
-def dummy_config():
-    return yaml.safe_load(
-        """
-        default:
-            trainer: ppo
-            batch_size: 32
-            beta: 5.0e-3
-            buffer_size: 512
-            epsilon: 0.2
-            gamma: 0.99
-            hidden_units: 128
-            lambd: 0.95
-            learning_rate: 3.0e-4
-            max_steps: 5.0e4
-            normalize: true
-            num_epoch: 5
-            num_layers: 2
-            time_horizon: 64
-            sequence_length: 64
-            summary_freq: 1000
-            use_recurrent: false
-            memory_size: 8
-            use_curiosity: false
-            curiosity_strength: 0.0
-            curiosity_enc_size: 1
-        """
-    )
-
-
-@pytest.fixture
 def basic_trainer_controller():
     return TrainerController(
         trainer_factory=None,
     tensorflow_set_seed.assert_called_with(seed)
 
 
-def trainer_controller_with_start_learning_mocks():
+@pytest.fixture
+def trainer_controller_with_start_learning_mocks(basic_trainer_controller):
     trainer_mock = MagicMock()
     trainer_mock.get_step = 0
     trainer_mock.get_max_steps = 5
-    tc = basic_trainer_controller()
+    tc = basic_trainer_controller
     tc.initialize_trainers = MagicMock()
     tc.trainers = {"testbrain": trainer_mock}
     tc.advance = MagicMock()
 
 
 @patch.object(tf, "reset_default_graph")
-def test_start_learning_trains_forever_if_no_train_model(tf_reset_graph):
-    tc, trainer_mock = trainer_controller_with_start_learning_mocks()
+def test_start_learning_trains_forever_if_no_train_model(
+    tf_reset_graph, trainer_controller_with_start_learning_mocks
+):
+    tc, trainer_mock = trainer_controller_with_start_learning_mocks
     tc.train_model = False
 
     tf_reset_graph.return_value = None
 
 
 @patch.object(tf, "reset_default_graph")
-def test_start_learning_trains_until_max_steps_then_saves(tf_reset_graph):
-    tc, trainer_mock = trainer_controller_with_start_learning_mocks()
+def test_start_learning_trains_until_max_steps_then_saves(
+    tf_reset_graph, trainer_controller_with_start_learning_mocks
+):
+    tc, trainer_mock = trainer_controller_with_start_learning_mocks
     tf_reset_graph.return_value = None
 
     brain_info_mock = MagicMock()
     tc._save_model.assert_called_once()
 
 
-def trainer_controller_with_take_step_mocks():
+@pytest.fixture
+def trainer_controller_with_take_step_mocks(basic_trainer_controller):
     trainer_mock = MagicMock()
     trainer_mock.get_step = 0
     trainer_mock.get_max_steps = 5
-    tc = basic_trainer_controller()
+    tc = basic_trainer_controller
-def test_take_step_adds_experiences_to_trainer_and_trains():
-    tc, trainer_mock = trainer_controller_with_take_step_mocks()
+def test_take_step_adds_experiences_to_trainer_and_trains(
+    trainer_controller_with_take_step_mocks
+):
+    tc, trainer_mock = trainer_controller_with_take_step_mocks
 
     brain_name = "testbrain"
     action_info_dict = {brain_name: MagicMock()}
     trainer_mock.increment_step.assert_called_once()
 
 
-def test_take_step_if_not_training():
-    tc, trainer_mock = trainer_controller_with_take_step_mocks()
+def test_take_step_if_not_training(trainer_controller_with_take_step_mocks):
+    tc, trainer_mock = trainer_controller_with_take_step_mocks
     tc.train_model = False
 
     brain_name = "testbrain"

ml-agents/mlagents/trainers/tests/test_trainer_util.py

 
 
 @pytest.fixture
-def dummy_config_with_override():
-    base = dummy_config()
+def dummy_config_with_override(dummy_config):
+    base = dummy_config
     base["testbrain"] = {}
     base["testbrain"]["normalize"] = False
     return base
 
 
 @patch("mlagents.trainers.brain.BrainParameters")
-def test_initialize_trainer_parameters_override_defaults(BrainParametersMock):
+def test_initialize_trainer_parameters_override_defaults(
+    BrainParametersMock, dummy_config_with_override
+):
     summaries_dir = "test_dir"
     run_id = "testrun"
     model_path = "model_dir"
     seed = 11
     expected_reward_buff_cap = 1
 
-    base_config = dummy_config_with_override()
+    base_config = dummy_config_with_override
     expected_config = base_config["default"]
     expected_config["summary_path"] = summaries_dir + f"/{run_id}_testbrain"
     expected_config["model_path"] = model_path + "/testbrain"
 
 
 @patch("mlagents.trainers.brain.BrainParameters")
-def test_initialize_ppo_trainer(BrainParametersMock):
+def test_initialize_ppo_trainer(BrainParametersMock, dummy_config):
     brain_params_mock = BrainParametersMock()
     BrainParametersMock.return_value.brain_name = "testbrain"
     external_brains = {"testbrain": BrainParametersMock()}
     seed = 11
     expected_reward_buff_cap = 1
 
-    base_config = dummy_config()
+    base_config = dummy_config
     expected_config = base_config["default"]
     expected_config["summary_path"] = summaries_dir + f"/{run_id}_testbrain"
     expected_config["model_path"] = model_path + "/testbrain"
 
 
 @patch("mlagents.trainers.brain.BrainParameters")
-def test_initialize_invalid_trainer_raises_exception(BrainParametersMock):
+def test_initialize_invalid_trainer_raises_exception(
+    BrainParametersMock, dummy_bad_config
+):
     summaries_dir = "test_dir"
     run_id = "testrun"
     model_path = "model_dir"
     seed = 11
-    bad_config = dummy_bad_config()
+    bad_config = dummy_bad_config
     BrainParametersMock.return_value.brain_name = "testbrain"
     external_brains = {"testbrain": BrainParametersMock()}
 
             trainers[brain_name] = trainer_factory.generate(brain_parameters)
 
 
-def test_handles_no_default_section():
+def test_handles_no_default_section(dummy_config):
-    config = dummy_config()
-    no_default_config = {brain_name: config["default"]}
+    no_default_config = {brain_name: dummy_config["default"]}
     brain_parameters = BrainParameters(
         brain_name=brain_name,
         vector_observation_space_size=1,
     trainer_factory.generate(brain_parameters)
 
 
-def test_raise_if_no_config_for_brain():
+def test_raise_if_no_config_for_brain(dummy_config):
-    config = dummy_config()
-    bad_config = {"some_other_brain": config["default"]}
+    bad_config = {"some_other_brain": dummy_config["default"]}
     brain_parameters = BrainParameters(
         brain_name=brain_name,
         vector_observation_space_size=1,

test_requirements.txt

 # Test-only dependencies should go here, not in setup.py
-pytest>=3.2.2,<4.0.0
+pytest>=3.2.2,<6.0.0
 pytest-cov==2.6.1