add unit test

tests/unit/clients/test_git.py

@@ -0,0 +1,19 @@
+import unittest
+from unittest.mock import MagicMock, patch
+
+from dbt.clients.git import list_tags
+
+
+class Git(unittest.TestCase):
+    @patch("dbt_common.clients.system.run_cmd")
+    @patch("subprocess.Popen")
+    def test_list_tags(self, mock_popen, mock_run_cmd):
+        mock_process = MagicMock()
+        mock_process.returncode = 0
+        mock_process.communicate.return_value = (b"v1.0.0\nv1.1.0\nv2.0.0\n", b"")
+        mock_popen.return_value = mock_process
+
+        cwd = "/path/to/repo"
+        tags = list_tags(cwd)
+
+        self.assertEqual(tags, ["v1.0.0", "v1.1.0", "v2.0.0"])