Add unit test for git integration

tests/test_git.py:
Add unit test for `git_changed_files()`.

tests/test_git.py

@@ -0,0 +1,45 @@
+from pathlib import Path
+from typing import List
+from typing import Optional
+from unittest.mock import Mock
+from unittest.mock import patch
+
+from pytest import mark
+
+from libkeyringctl import git
+
+
+@mark.parametrize(
+    "git_path, base, paths",
+    [
+        (None, None, None),
+        (Path("git_path"), None, None),
+        (Path("git_path"), "base", None),
+        (Path("git_path"), "base", [Path("foo"), Path("bar")]),
+    ],
+)
+@patch("libkeyringctl.git.system")
+def test_git_changed_files(
+    system_mock: Mock,
+    git_path: Optional[Path],
+    base: Optional[str],
+    paths: Optional[List[Path]],
+) -> None:
+    system_mock.return_value = "create some thing foo\n" "delete some thing bar\n" "some thing baz\n"
+
+    assert git.git_changed_files(git_path=git_path, base=base, paths=paths) == (
+        [Path("foo")],
+        [Path("bar")],
+        [Path("baz")],
+    )
+
+    name, args, kwargs = system_mock.mock_calls[0]
+    if git_path:
+        assert "-C" in args[0]
+        assert str(git_path) in args[0]
+    if base:
+        assert base in args[0]
+    if paths:
+        assert "--" in args[0]
+        for path in paths:
+            assert str(path) in args[0]