Add download_model test checking for invalid paths.

tests-unit/prompt_server_test/download_models_test.py

@@ -149,6 +149,28 @@ async def test_download_model_url_request_failure():
     # Verify that the get method was called with the correct URL
     mock_get.assert_called_once_with('http://example.com/model.safetensors')
 
+@pytest.mark.asyncio
+async def test_download_model_invalid_model_subdirectory():
+    
+    mock_make_request = AsyncMock()
+    mock_progress_callback = AsyncMock()
+
+    
+    result = await download_model(
+        mock_make_request,
+        'model.bin',
+        'http://example.com/model.bin',
+        '../bad_path',
+        mock_progress_callback
+    )
+
+    # Assert the result
+    assert isinstance(result, DownloadModelResult)
+    assert result.message == 'Invalid model subdirectory'
+    assert result.status == 'error'
+    assert result.already_existed is False
+
+
 # For create_model_path function
 def test_create_model_path(tmp_path, monkeypatch):
     mock_models_dir = tmp_path / "models"