Fix tests' resilience to missing optional dependencies.

- Run `Aggregator` unit tests for available frameworks only.
- Skip `gRPC`-dedicated tests when grpc is not installed.
- Skip `DPTrainingManager` tests when opacus is not installed.
- Fix toy regression functional tests failing when some frameworks
  are missing due to the use of too-specific type hints.

test/aggregator/test_aggregator.py

@@ -17,7 +17,6 @@
 
 """Unit tests for the 'Aggregator' subclasses."""
 
-import typing
 from typing import Dict, Type
 
 import pytest
@@ -29,12 +28,13 @@ from declearn.test_utils import (
     GradientsTestCase,
     assert_dict_equal,
     assert_json_serializable_dict,
+    list_available_frameworks,
 )
 from declearn.utils import set_device_policy
 
 
 AGGREGATOR_CLASSES = list_aggregators()
-VECTOR_FRAMEWORKS = typing.get_args(FrameworkType)
+VECTOR_FRAMEWORKS = list_available_frameworks()
 
 
 @pytest.fixture(name="updates")

test/communication/test_grpc.py

@@ -31,10 +31,14 @@ import asyncio
 import uuid
 from typing import AsyncIterator, Dict, Iterator
 
-import grpc  # type: ignore
 import pytest
 import pytest_asyncio
 
+try:
+    import grpc  # type: ignore
+except ModuleNotFoundError:
+    pytest.skip("GRPC is unavailable", allow_module_level=True)
+
 from declearn.communication.api.backend.actions import Ping
 from declearn.communication.grpc._server import load_pem_file
 from declearn.communication.grpc import GrpcClient, GrpcServer

test/functional/test_toy_reg.py

@@ -67,7 +67,6 @@ from declearn.utils import set_device_policy
 
 # optional frameworks' dependencies pylint: disable=ungrouped-imports
 # pylint: disable=duplicate-code
-# false-positives; pylint: disable=no-member
 
 # tensorflow imports
 try:
@@ -104,7 +103,8 @@ else:
         return (y_pred - y_true) ** 2
 
 
-# pylint: disable=duplicate-code
+# pylint: enable=duplicate-code, ungrouped-imports
+
 
 SEED = 0
 R2_THRESHOLD = 0.9999
@@ -124,7 +124,7 @@ def get_model(framework: FrameworkType) -> Model:
     raise ValueError(f"Unrecognised model framework: '{framework}'.")
 
 
-def _get_model_numpy() -> SklearnSGDModel:
+def _get_model_numpy() -> Model:
     """Return a linear model with MSE loss in Sklearn, with zero weights."""
     np.random.seed(SEED)  # set seed
     model = SklearnSGDModel.from_parameters(
@@ -133,10 +133,12 @@ def _get_model_numpy() -> SklearnSGDModel:
     return model
 
 
-def _get_model_tflow() -> TensorflowModel:
+def _get_model_tflow() -> Model:
     """Return a linear model with MSE loss in TensorFlow, with zero weights."""
     tf.random.set_seed(SEED)  # set seed
-    tfmod = tf.keras.Sequential(tf.keras.layers.Dense(units=1))
+    tfmod = tf.keras.Sequential(  # pylint: disable=no-member
+        tf.keras.layers.Dense(units=1)  # pylint: disable=no-member
+    )
     tfmod.build([None, 100])
     model = TensorflowModel(tfmod, loss="mean_squared_error")
     with tf.device("CPU"):
@@ -148,7 +150,7 @@ def _get_model_tflow() -> TensorflowModel:
     return model
 
 
-def _get_model_torch() -> TorchModel:
+def _get_model_torch() -> Model:
     """Return a linear model with MSE loss in Torch, with zero weights."""
     torch.manual_seed(SEED)  # set seed
     torchmod = torch.nn.Sequential(
@@ -164,7 +166,7 @@ def _get_model_torch() -> TorchModel:
     return model
 
 
-def _get_model_haiku() -> HaikuModel:
+def _get_model_haiku() -> Model:
     """Return a linear model with MSE loss in Haiku, with zero weights."""
     model = HaikuModel(haiku_model_fn, loss=haiku_loss_fn)
     model.initialize({"data_type": "float32", "features_shape": (100,)})
@@ -427,6 +429,9 @@ async def async_run_client(
     await client.async_run()
 
 
+# similar structure in other functional tests; pylint: disable=duplicate-code
+
+
 @pytest.mark.asyncio
 async def test_declearn_federated(
     framework: FrameworkType,

test/main/test_train_manager_dp.py

@@ -21,8 +21,12 @@ import os
 from typing import Any, Optional
 
 import pytest
-from opacus.accountants import RDPAccountant  # type: ignore
-from opacus.accountants.utils import get_noise_multiplier  # type: ignore
+
+try:
+    from opacus.accountants import RDPAccountant  # type: ignore
+    from opacus.accountants.utils import get_noise_multiplier  # type: ignore
+except ModuleNotFoundError:
+    pytest.skip("Opacus is unavailable", allow_module_level=True)
 
 from declearn.communication import messaging
 from declearn.dataset import DataSpecs