test: add CLI integration tests for main function

- Test -d flag calls download_set with correct set ID
- Test -l flag calls print_sets with username
- Test -i flag calls download_photo with correct photo ID
- Test _init failure returns exit code 1

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: beaufour

tests/test_main.py

@@ -3,7 +3,7 @@
 This ensures that all the dependencies actually load too.
 """
 
-from unittest.mock import patch
+from unittest.mock import Mock, patch
 
 from flickr_download.flick_download import main
 
@@ -30,3 +30,69 @@ def test_main_list_naming() -> None:
     with patch("sys.argv", ["flickr_download", "--list_naming"]):
         result = main()
         assert result == 1
+
+
+@patch("flickr_download.flick_download._init")
+@patch("flickr_download.flick_download.download_set")
+def test_main_download_set(mock_download: Mock, mock_init: Mock) -> None:
+    """Main with -d downloads a set."""
+    mock_init.return_value = True
+
+    with (
+        patch("sys.argv", ["flickr_download", "-k", "key", "-s", "secret", "-d", "12345"]),
+        patch("flickr_download.flick_download._load_defaults", return_value={}),
+    ):
+        result = main()
+
+    assert result == 0
+    mock_download.assert_called_once()
+    call_args = mock_download.call_args
+    assert call_args[0][0] == "12345"  # set_id
+
+
+@patch("flickr_download.flick_download._init")
+@patch("flickr_download.flick_download.print_sets")
+def test_main_list_sets(mock_print: Mock, mock_init: Mock) -> None:
+    """Main with -l lists sets for user."""
+    mock_init.return_value = True
+
+    with (
+        patch("sys.argv", ["flickr_download", "-k", "key", "-s", "secret", "-l", "testuser"]),
+        patch("flickr_download.flick_download._load_defaults", return_value={}),
+    ):
+        result = main()
+
+    assert result == 0
+    mock_print.assert_called_once_with("testuser")
+
+
+@patch("flickr_download.flick_download._init")
+@patch("flickr_download.flick_download.download_photo")
+def test_main_download_photo(mock_download: Mock, mock_init: Mock) -> None:
+    """Main with -i downloads a single photo."""
+    mock_init.return_value = True
+
+    with (
+        patch("sys.argv", ["flickr_download", "-k", "key", "-s", "secret", "-i", "99999"]),
+        patch("flickr_download.flick_download._load_defaults", return_value={}),
+    ):
+        result = main()
+
+    assert result == 0
+    mock_download.assert_called_once()
+    call_args = mock_download.call_args
+    assert call_args[0][0] == "99999"  # photo_id
+
+
+@patch("flickr_download.flick_download._init")
+def test_main_init_failure(mock_init: Mock) -> None:
+    """Main returns 1 when _init fails."""
+    mock_init.return_value = False
+
+    with (
+        patch("sys.argv", ["flickr_download", "-k", "key", "-s", "secret", "-d", "12345"]),
+        patch("flickr_download.flick_download._load_defaults", return_value={}),
+    ):
+        result = main()
+
+    assert result == 1