Split out Flat generator to be able to test it

tests/tree_test.py

@@ -31,6 +31,20 @@ class TestTreeMethods(unittest.TestCase):
         with open(path, "r") as f:
             data = yaml.safe_load(f)
         self.assertEqual(data, revisions.as_list())
+
+        # verify flat lists
+        path = os.path.join(
+            os.path.dirname(__file__), f"fixtures/{package}-expected-list.yaml"
+        )
+        flat_list = [str(x) for x in revisions.as_flat_list()]
+        if os.getenv("REGENERATE_DATA"):
+            with open(path, "w") as f:
+                yaml.dump(flat_list, f)
+
+        with open(path, "r") as f:
+            data = yaml.safe_load(f)
+        self.assertEqual(data, flat_list)
+
         self.db.conn.rollback()
 
     def test_zsh_tree(self):