fix: remove network dependency from test_download

Replace the CI-only skip with a fully mocked CCXT exchange so the
download test reads from local CSV data in tests/resources/test_data/ohlcv
instead of making network calls.

Author: MDUYN

tests/test_download.py

@@ -2,24 +2,41 @@
 import unittest
 from pathlib import Path
 from unittest import TestCase
+from unittest.mock import patch, MagicMock
 from datetime import datetime, timezone
 
-from investing_algorithm_framework import download
+import polars as pl
 
+from investing_algorithm_framework import download
 
 
 class TestDownload(TestCase):
 
-    @unittest.skipIf(os.environ.get("CI"), "Requires pre-downloaded data")
-    def test_download_data_with_already_existing_data(self):
-        storage_path = Path(__file__).parent / "resources" / "data"
+    @patch("investing_algorithm_framework.infrastructure"
+           ".data_providers.ccxt.ccxt")
+    def test_download_data_with_already_existing_data(self, mock_ccxt_module):
+        """
+        Test that download() works when local CSV data already exists.
+        Uses test_data/ohlcv CSVs; CCXT is mocked so no network call
+        is made (the provider reads from the local file).
+        """
+        # Mock the exchange so has_data() succeeds without network
+        mock_exchange = MagicMock()
+        mock_exchange.load_markets.return_value = {"BTC/EUR": {}}
+        mock_exchange.timeframes = {"2h": "2h"}
+        mock_exchange_class = MagicMock(return_value=mock_exchange)
+        mock_ccxt_module.bitvavo = mock_exchange_class
+
+        storage_path = (
+            Path(__file__).parent / "resources" / "test_data" / "ohlcv"
+        )
         data = download(
             symbol="BTC/EUR",
             market="BITVAVO",
             data_type="OHLCV",
             time_frame="2h",
-            start_date=datetime(2023, 1, 1, tzinfo=timezone.utc),
-            end_date=datetime(2023, 12, 31, tzinfo=timezone.utc),
+            start_date=datetime(2023, 8, 11, 16, 0, tzinfo=timezone.utc),
+            end_date=datetime(2023, 12, 2, 0, 0, tzinfo=timezone.utc),
             storage_path=str(storage_path)
         )
         self.assertIsNotNone(data)