Test snapshot image is generated

tests/unit_tests/test_simulated_camera.py

@@ -2,11 +2,13 @@
 
 import logging
 import time
+from io import BytesIO
 
 import numpy as np
 import pytest
 from hypothesis import given
 from hypothesis import strategies as st
+from PIL import Image
 from pydantic import ValidationError
 
 import labthings_fastapi as lt
@@ -44,6 +46,19 @@ def stage(test_env) -> lt.Thing:
     return test_env.get_thing_by_type(DummyStage)
 
 
+def test_snapshot(test_env) -> lt.Thing:
+    """Check the snapshot GET request returns an image."""
+    http_client = test_env.get_thing_client("camera").client
+    response = http_client.get("camera/snapshot")
+    response.raise_for_status()
+    assert response.headers["content-type"] == "image/jpeg"
+    image = Image.open(BytesIO(response.content))
+
+    assert image.format == "JPEG"
+    assert image.width == 320
+    assert image.height == 240
+
+
 def test_downsample_shape_2d():
     """Test downsampling for 2D array."""
     shape_2d = (100, 80)