fix(tests): download scenes in top conf. and add thread Lock

python/differt/plotting/_utils.py

@@ -6,8 +6,12 @@
 from collections.abc import MutableMapping
 from contextlib import AbstractContextManager, contextmanager
 from functools import wraps
+from threading import Lock
 from typing import TYPE_CHECKING, Any, Callable, Generic, Protocol, TypeVar
 
+BACKEND_LOCK = Lock()
+"""A Lock to avoid modifying backend (and defaults) in multiple threads at the same time (e.g., with Pytest."""
+
 DEFAULT_BACKEND = "vispy"
 SUPPORTED_BACKENDS = ("vispy", "matplotlib", "plotly")
 
@@ -93,15 +97,16 @@ def set_defaults(backend: str | None = None, **kwargs: Any) -> str:
             f"We currently support: {', '.join(SUPPORTED_BACKENDS)}."
         )
 
-    try:
-        importlib.import_module(f"{backend}")
-        DEFAULT_BACKEND = backend
-        DEFAULT_KWARGS = kwargs
-        return backend
-    except ImportError:
-        raise ImportError(
-            f"Could not load backend '{backend}', did you install it?"
-        ) from None
+    with BACKEND_LOCK:
+        try:
+            importlib.import_module(f"{backend}")
+            DEFAULT_BACKEND = backend
+            DEFAULT_KWARGS = kwargs
+            return backend
+        except ImportError:
+            raise ImportError(
+                f"Could not load backend '{backend}', did you install it?"
+            ) from None
 
 
 @contextmanager

tests/conftest.py

@@ -2,6 +2,12 @@
 
 import pytest
 
+from differt.scene.sionna import download_sionna_scenes
+
+
+def pytest_sessionstart(session: pytest.Session) -> None:
+    download_sionna_scenes()
+
 
 @pytest.fixture(scope="session")
 def test_dir() -> Path:

tests/rt/test_graph.py

@@ -19,9 +19,10 @@ def test_insert_from_and_to_nodes(self) -> None:
         assert from_ == 9
         assert to == 10
 
-        with pytest.raises(TypeError) as exc:
+        with pytest.raises(
+            TypeError, match="takes 0 positional arguments but 1 was given"
+        ):
             _ = graph.insert_from_and_to_nodes(True)  # type: ignore
-        assert "takes 0 positional arguments but 1 was given" in str(exc)
 
     def test_from_graph(self) -> None:
         graph = CompleteGraph(10)
@@ -32,9 +33,10 @@ def test_from_graph(self) -> None:
     def test_all_keyword_only_parameters(self) -> None:
         graph = DiGraph.from_complete_graph(CompleteGraph(5))
 
-        with pytest.raises(TypeError) as exc:
+        with pytest.raises(
+            TypeError, match="takes 3 positional arguments but 4 were given"
+        ):
             _ = graph.all_paths(0, 1, 0, True)  # type: ignore
-            assert "takes 3 positional arguments but 4 were given" in str(exc)
 
     @pytest.mark.parametrize(
         "num_nodes,depth",

tests/scene/test_sionna.py

@@ -5,11 +5,9 @@
 
 @pytest.mark.parametrize("scene_name", ("foo", "bar"))
 def test_get_unexisting_sionna_scene(scene_name: str) -> None:
-    with pytest.raises(ValueError) as exc:
+    with pytest.raises(ValueError, match="Cannot find scene_name"):
         _ = get_sionna_scene(scene_name)
 
-    assert "Cannot find scene_name" in str(exc)
-
 
 class TestSionnaScene:
     @pytest.mark.parametrize("scene_name", list_sionna_scenes())