Rearrange Picamera tests to start using server context manager.

hardware-specific-tests/picamera2/cam_test_utils/__init__.py

@@ -0,0 +1,36 @@
+"""Utilities to help with testing the camera."""
+
+from typing import Optional
+import tempfile
+
+from contextlib import contextmanager
+
+from fastapi.testclient import TestClient
+
+from labthings_fastapi.server import ThingServer
+from labthings_fastapi.client import ThingClient
+
+from openflexure_microscope_server.things.camera.picamera import StreamingPiCamera2
+
+
+@contextmanager
+def camera_test_client(settings_folder: Optional[str] = None):
+    """Yield a camera ThingClient on a camera server.
+
+    This is a context manager not a pytest fixture as it needs to be created
+    multiple times in some tests.
+    """
+    # Create a temp dir, if the setting folder is set it isn't really needed
+    # but doesn't add much overhead.
+    with tempfile.TemporaryDirectory() as tmpdir:
+        if settings_folder is None:
+            settings_folder = tmpdir
+        cam = StreamingPiCamera2()
+        server = ThingServer(settings_folder=settings_folder)
+        server.add_thing(cam, "/camera/")
+
+        with TestClient(server.app) as test_client:
+            client = ThingClient.from_url("/camera/", client=test_client)
+            yield client
+    del server
+    del cam