update drop index test

Author: tswast

tests/unit/conftest.py

@@ -0,0 +1,24 @@
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import pytest
+
+
+@pytest.fixture(scope="session")
+def polars_session():
+    pytest.importorskip("polars")
+
+    from bigframes.testing import polars_session
+
+    return polars_session.TestSession()

tests/unit/core/test_groupby.py

@@ -23,14 +23,6 @@
 pytest.importorskip("pandas", minversion="2.0.0")
 
 
-# All tests in this file require polars to be installed to pass.
-@pytest.fixture(scope="module")
-def polars_session():
-    from bigframes.testing import polars_session
-
-    return polars_session.TestSession()
-
-
 def test_groupby_df_iter_by_key_singular(polars_session):
     pd_df = pd.DataFrame({"colA": ["a", "a", "b", "c", "c"], "colB": [1, 2, 3, 4, 5]})
     bf_df = bpd.DataFrame(pd_df, session=polars_session)

tests/unit/test_dataframe.py

@@ -13,9 +13,11 @@
 # limitations under the License.
 
 import google.cloud.bigquery
+import pandas as pd
 import pytest
 
 import bigframes.dataframe
+import bigframes.session
 from bigframes.testing import mocks
 
 
@@ -138,14 +140,17 @@ def test_dataframe_drop_columns_inplace_returns_none(monkeypatch: pytest.MonkeyP
     assert dataframe.columns.to_list() == ["col2"]
 
 
-def test_dataframe_drop_index_inplace_returns_none(monkeypatch: pytest.MonkeyPatch):
-    dataframe = mocks.create_dataframe(
-        monkeypatch, data={"col1": [1, 2, 3], "index_col": [0, 1, 2]}
-    ).set_index("index_col")
-    # TODO(swast): Support dataframe.index.to_list()
-    # assert dataframe.index.to_list() == [0, 1, 2]
+def test_dataframe_drop_index_inplace_returns_none(
+    # Drop index depends on the actual data, not just metadata, so use the
+    # local engine for more robust testing.
+    polars_session: bigframes.session.Session,
+):
+    dataframe = polars_session.read_pandas(
+        pd.DataFrame({"col1": [1, 2, 3], "index_col": [0, 1, 2]}).set_index("index_col")
+    )
+    assert dataframe.index.to_list() == [0, 1, 2]
     assert dataframe.drop(index=[0, 2], inplace=True) is None
-    # assert dataframe.index.to_list() == [1]
+    assert dataframe.index.to_list() == [1]
 
 
 def test_dataframe_drop_columns_returns_new_dataframe(monkeypatch: pytest.MonkeyPatch):

tests/unit/test_local_engine.py

@@ -24,14 +24,6 @@
 pytest.importorskip("pandas", minversion="2.0.0")
 
 
-# All tests in this file require polars to be installed to pass.
-@pytest.fixture(scope="module")
-def polars_session():
-    from bigframes.testing import polars_session
-
-    return polars_session.TestSession()
-
-
 @pytest.fixture(scope="module")
 def small_inline_frame() -> pd.DataFrame:
     df = pd.DataFrame(