coverage

tests/utils_test.py

@@ -8,6 +8,7 @@
 from pandas.testing import assert_series_equal
 
 import narwhals.stable.v1 as nw
+from narwhals._pandas_like.utils import reset_index_no_copy
 from tests.utils import PANDAS_VERSION
 from tests.utils import get_module_version_as_tuple
 
@@ -147,3 +148,14 @@ def test_maybe_convert_dtypes_polars() -> None:
 def test_get_trivial_version_with_uninstalled_module() -> None:
     result = get_module_version_as_tuple("non_existent_module")
     assert result == (0, 0, 0)
+
+
+def test_reset_index_no_copy() -> None:
+    df = pd.DataFrame({"a": [1, 2, 3], "b": [4.0, 5.0, 6.0]}).set_index("a")
+    reset_index_no_copy(df, pd)
+    pd.testing.assert_frame_equal(
+        df, pd.DataFrame({"b": [4.0, 5.0, 6.0], "a": [1, 2, 3]})
+    )
+    df.index.name = "b"
+    with pytest.raises(ValueError, match="Cannot insert column"):
+        reset_index_no_copy(df, pd)