Fix process_video and add test case

test/utils/test_video.py

@@ -0,0 +1,29 @@
+import cv2
+import numpy as np
+
+from supervision.utils.video import process_video
+
+
+def _create_test_video(path, num_frames, width=20, height=10):
+    fourcc = cv2.VideoWriter_fourcc(*"mp4v")
+    out = cv2.VideoWriter(path, fourcc, 1.0, (width, height))
+
+    for _ in range(num_frames):
+        frame = np.zeros((height, width, 3), dtype=np.uint8)
+        out.write(frame)
+
+    out.release()
+
+
+def test_process_video_max_frames_exceeds_total_frames(tmp_path):
+    source_path = tmp_path / "source.mp4"
+    target_path = tmp_path / "target.mp4"
+
+    _create_test_video(str(source_path), num_frames=5)
+
+    process_video(
+        source_path=str(source_path),
+        target_path=str(target_path),
+        callback=lambda frame, _: frame,
+        max_frames=10,
+    )