diff --git a/perceptionmetrics/utils/detection_metrics.py b/perceptionmetrics/utils/detection_metrics.py
index f76505dc..6da89f18 100644
--- a/perceptionmetrics/utils/detection_metrics.py
+++ b/perceptionmetrics/utils/detection_metrics.py
@@ -297,7 +297,7 @@ def get_overall_precision_recall_curve(self) -> Dict[str, List[float]]:
             return {"precision": [0.0], "recall": [0.0]}
 
         fn_count = sum(1 for d in all_detections if d[1] == -1)
-        
+
         # Sort by score
         all_detections = sorted(
             [d for d in all_detections if d[0] is not None], key=lambda x: -x[0]
diff --git a/tests/conftest.py b/tests/conftest.py
new file mode 100644
index 00000000..a05c4a1b
--- /dev/null
+++ b/tests/conftest.py
@@ -0,0 +1,5 @@
+# tests/conftest.py
+# Pre-import open3d before any test module is collected.
+# test_yolo.py stubs open3d only if it's NOT already in sys.modules.
+# Loading it here first ensures test_lidar.py gets the real open3d.
+import open3d  # noqa: F401
diff --git a/tests/test_lidar.py b/tests/test_lidar.py
index c94f57a6..a8fd31b3 100644
--- a/tests/test_lidar.py
+++ b/tests/test_lidar.py
@@ -206,7 +206,7 @@ def test_build_point_cloud(self, sample_points, sample_colors):
         """Test build_point_cloud creates proper Open3D point cloud."""
         point_cloud = build_point_cloud(sample_points, sample_colors)
 
-        assert isinstance(point_cloud, o3d.geometry.PointCloud)
+        assert type(point_cloud).__name__ == "PointCloud"
         assert len(point_cloud.points) == len(sample_points)
         assert len(point_cloud.colors) == len(sample_colors)
         assert np.allclose(np.asarray(point_cloud.points), sample_points)
@@ -220,7 +220,7 @@ def test_view_point_cloud(self, mock_draw, sample_points, sample_colors):
         mock_draw.assert_called_once()
         args = mock_draw.call_args[0][0]
         assert len(args) == 1
-        assert isinstance(args[0], o3d.geometry.PointCloud)
+        assert type(args[0]).__name__ == "PointCloud"
 
     @patch("open3d.visualization.rendering.OffscreenRenderer")
     def test_render_point_cloud(
diff --git a/tests/test_yolo.py b/tests/test_yolo.py
index 2fc45fe9..87e13296 100644
--- a/tests/test_yolo.py
+++ b/tests/test_yolo.py
@@ -4,6 +4,18 @@
 
 import pandas as pd
 
+# ---------------------------------------------------------------------------
+# Try importing real optional C-extensions first so they get cached in
+# sys.modules. This prevents the stub block below from replacing a real
+# library that IS available in the environment (e.g. open3d), which would
+# otherwise leak a MagicMock into other test modules like test_lidar.py.
+# ---------------------------------------------------------------------------
+for _real in ("open3d", "supervision"):
+    try:
+        __import__(_real)
+    except ImportError:
+        pass
+
 # ---------------------------------------------------------------------------
 # Stub out heavy optional C-extensions that are not available in the test
 # environment (open3d, tqdm, etc.) before importing any perceptionmetrics module.