(DiamondLightSource/hyperion#1343) Address review comments

src/dodal/devices/areadetector/plugins/MJPG.py

@@ -40,10 +40,10 @@ def _save_image(self, image: Image.Image):
         and filename signals. The full resultant path is put on the last_saved_path signal
         """
         filename_str = self.filename.get()
-        directory_str = Path(self.directory.get())  # type: ignore
+        directory_str: str = self.directory.get()  # type: ignore
 
         path = Path(f"{directory_str}/{filename_str}.png").as_posix()
-        if not os.path.isdir(directory_str):
+        if not os.path.isdir(Path(directory_str)):
             LOGGER.info(f"Snapshot folder {directory_str} does not exist, creating...")
             os.mkdir(directory_str)
 

tests/devices/unit_tests/test_oav.py

@@ -1,4 +1,3 @@
-from pathlib import PosixPath
 from unittest.mock import MagicMock, call, patch
 
 import numpy as np
@@ -94,7 +93,7 @@ def test_given_directory_not_existing_when_snapshot_triggered_then_directory_cre
     mock_os.path.isdir.return_value = False
     st = fake_oav.grid_snapshot.trigger()
     st.wait()
-    mock_os.mkdir.assert_called_once_with(PosixPath("test directory"))
+    mock_os.mkdir.assert_called_once_with("test directory")
 
 
 @patch("requests.get")