Add unit tests on model_path usage in Engine init

tests/test_engine.py

@@ -3,6 +3,8 @@
 import time
 from datetime import datetime, timezone
 from pathlib import Path
+import pytest
+from unittest.mock import patch
 
 from dotenv import load_dotenv
 from PIL import Image
@@ -77,6 +79,29 @@ def test_engine_offline(tmpdir_factory, mock_wildfire_image, mock_forest_image):
     assert engine._states["-1"]["last_predictions"][2][3] < datetime.now().isoformat()
     assert engine._states["-1"]["last_predictions"][2][4] is False
 
+# Testing the behavior Engine instanciation with model_path as input
+
+# mock_isfile is a mock of the os.path.isfile() function which allows to simulate file existence
+@patch("os.path.isfile")
+def test_valid_model_path(mock_isfile):
+    '''Tests Engine instanciation with a valid input model_path'''
+    mock_isfile.return_value = True  # Simulates file existence
+    instance = Engine(model_path="model.onnx")
+    assert instance.format == "onnx"
+
+@patch("os.path.isfile")
+def test_nonexistent_model(mock_isfile):
+    '''Tests Engine instanciation with a non-existent input model_path'''
+    mock_isfile.return_value = False # Simulates file non-existence
+    with pytest.raises(ValueError, match=r"Model file not found: .*"):
+        Engine(model_path="nonexistent.onnx")
+
+@patch("os.path.isfile")
+def test_invalid_extension(mock_isfile):
+    '''Tests Engine instanciation with a file format different than .onnx'''
+    mock_isfile.return_value = True  # Simulates file existence
+    with pytest.raises(ValueError, match=r"Input model_path should point toward an onnx export but currently is *"):
+        Engine(model_path="model.ncnn")
 
 def test_engine_online(tmpdir_factory, mock_wildfire_stream, mock_wildfire_image):
     # Cache