TST: Add regression tests for enlarging MultiIndex with None keys (GH#59153)

Author: wdyy20041223

pandas/tests/indexing/multiindex/test_setitem.py

@@ -505,7 +505,7 @@ def test_setitem_enlargement_multiindex_with_none(self):
         # Verify the shape and values
         assert df.shape == (5, 2)
         assert list(df.iloc[-1]) == [12.0, 13.0]
-        
+
         # Verify we can retrieve the newly added row using None
         result = df.loc[("A", None), :]
         expected_row = Series([12.0, 13.0], index=[0, 1], name=("A", np.nan))
@@ -527,12 +527,12 @@ def test_setitem_enlargement_multiindex_multiple_none(self):
         assert df.shape == (4, 2)
         assert list(df.iloc[2]) == [5.0, 6.0]
         assert list(df.iloc[3]) == [7.0, 8.0]
-        
+
         # Verify we can retrieve rows with None keys using np.nan
         result = df.loc[(np.nan, "c1"), :]
         expected_row = Series([5.0, 6.0], index=["x", "y"], name=(np.nan, "c1"))
         tm.assert_series_equal(result, expected_row)
-        
+
         result = df.loc[("C", np.nan), :]
         expected_row = Series([7.0, 8.0], index=["x", "y"], name=("C", np.nan))
         tm.assert_series_equal(result, expected_row)