CoW: Remove remaining cow occurrences from tests (#57477)

Author: phofl

pandas/conftest.py

@@ -1987,14 +1987,6 @@ def indexer_ial(request):
     return request.param
 
 
-@pytest.fixture
-def using_copy_on_write() -> bool:
-    """
-    Fixture to check if Copy-on-Write is enabled.
-    """
-    return True
-
-
 @pytest.fixture
 def using_infer_string() -> bool:
     """

pandas/tests/copy_view/test_functions.py

@@ -89,16 +89,6 @@ def test_preserve_getitem(self):
         assert df.loc[[0]].flags.allows_duplicate_labels is False
         assert df.loc[0, ["A"]].flags.allows_duplicate_labels is False
 
-    def test_ndframe_getitem_caching_issue(self, request, using_copy_on_write):
-        if not using_copy_on_write:
-            request.applymarker(pytest.mark.xfail(reason="Unclear behavior."))
-        # NDFrame.__getitem__ will cache the first df['A']. May need to
-        # invalidate that cache? Update the cached entries?
-        df = pd.DataFrame({"A": [0]}).set_flags(allows_duplicate_labels=False)
-        assert df["A"].flags.allows_duplicate_labels is False
-        df.flags.allows_duplicate_labels = True
-        assert df["A"].flags.allows_duplicate_labels is True
-
     @pytest.mark.parametrize(
         "objs, kwargs",
         [

pandas/tests/copy_view/test_methods.py

@@ -12,7 +12,7 @@
 
 
 class TestPeriodIndex:
-    def test_getitem_periodindex_duplicates_string_slice(self, using_copy_on_write):
+    def test_getitem_periodindex_duplicates_string_slice(self):
         # monotonic
         idx = PeriodIndex([2000, 2007, 2007, 2009, 2009], freq="Y-JUN")
         ts = Series(np.random.default_rng(2).standard_normal(len(idx)), index=idx)
@@ -22,10 +22,7 @@ def test_getitem_periodindex_duplicates_string_slice(self, using_copy_on_write):
         expected = ts[1:3]
         tm.assert_series_equal(result, expected)
         result[:] = 1
-        if using_copy_on_write:
-            tm.assert_series_equal(ts, original)
-        else:
-            assert (ts[1:3] == 1).all()
+        tm.assert_series_equal(ts, original)
 
         # not monotonic
         idx = PeriodIndex([2000, 2007, 2007, 2009, 2007], freq="Y-JUN")

pandas/tests/generic/test_duplicate_labels.py

@@ -32,7 +32,7 @@
 
 class TestCommon:
     @pytest.mark.parametrize("name", [None, "new_name"])
-    def test_to_frame(self, name, index_flat, using_copy_on_write):
+    def test_to_frame(self, name, index_flat):
         # see GH#15230, GH#22580
         idx = index_flat
 
@@ -46,8 +46,6 @@ def test_to_frame(self, name, index_flat, using_copy_on_write):
         assert df.index is idx
         assert len(df.columns) == 1
         assert df.columns[0] == idx_name
-        if not using_copy_on_write:
-            assert df[idx_name].values is not idx.values
 
         df = idx.to_frame(index=False, name=idx_name)
         assert df.index is not idx

pandas/tests/indexes/period/test_partial_slicing.py

@@ -753,7 +753,7 @@ def test_reindex_items(self):
             mgr.iget(3).internal_values(), reindexed.iget(3).internal_values()
         )
 
-    def test_get_numeric_data(self, using_copy_on_write):
+    def test_get_numeric_data(self):
         mgr = create_mgr(
             "int: int; float: float; complex: complex;"
             "str: object; bool: bool; obj: object; dt: datetime",
@@ -774,18 +774,12 @@ def test_get_numeric_data(self, using_copy_on_write):
             np.array([100.0, 200.0, 300.0]),
             inplace=True,
         )
-        if using_copy_on_write:
-            tm.assert_almost_equal(
-                mgr.iget(mgr.items.get_loc("float")).internal_values(),
-                np.array([1.0, 1.0, 1.0]),
-            )
-        else:
-            tm.assert_almost_equal(
-                mgr.iget(mgr.items.get_loc("float")).internal_values(),
-                np.array([100.0, 200.0, 300.0]),
-            )
+        tm.assert_almost_equal(
+            mgr.iget(mgr.items.get_loc("float")).internal_values(),
+            np.array([1.0, 1.0, 1.0]),
+        )
 
-    def test_get_bool_data(self, using_copy_on_write):
+    def test_get_bool_data(self):
         mgr = create_mgr(
             "int: int; float: float; complex: complex;"
             "str: object; bool: bool; obj: object; dt: datetime",
@@ -801,16 +795,10 @@ def test_get_bool_data(self, using_copy_on_write):
         )
 
         bools.iset(0, np.array([True, False, True]), inplace=True)
-        if using_copy_on_write:
-            tm.assert_numpy_array_equal(
-                mgr.iget(mgr.items.get_loc("bool")).internal_values(),
-                np.array([True, True, True]),
-            )
-        else:
-            tm.assert_numpy_array_equal(
-                mgr.iget(mgr.items.get_loc("bool")).internal_values(),
-                np.array([True, False, True]),
-            )
+        tm.assert_numpy_array_equal(
+            mgr.iget(mgr.items.get_loc("bool")).internal_values(),
+            np.array([True, True, True]),
+        )
 
     def test_unicode_repr_doesnt_raise(self):
         repr(create_mgr("b,\u05d0: object"))

pandas/tests/indexes/test_common.py

@@ -438,7 +438,7 @@ def test_context_manageri_user_provided(all_parsers, datapath):
 
 
 @skip_pyarrow  # ParserError: Empty CSV file
-def test_file_descriptor_leak(all_parsers, using_copy_on_write):
+def test_file_descriptor_leak(all_parsers):
     # GH 31488
     parser = all_parsers
     with tm.ensure_clean() as path:

pandas/tests/internals/test_internals.py

@@ -8,8 +8,6 @@
 import numpy as np
 import pytest
 
-from pandas._config import using_copy_on_write
-
 from pandas.compat import is_platform_windows
 from pandas.compat.pyarrow import (
     pa_version_under11p0,
@@ -425,15 +423,10 @@ def test_read_filters(self, engine, tmp_path):
             repeat=1,
         )
 
-    def test_write_index(self, engine, using_copy_on_write, request):
-        check_names = engine != "fastparquet"
-        if using_copy_on_write and engine == "fastparquet":
-            request.applymarker(
-                pytest.mark.xfail(reason="fastparquet write into index")
-            )
-
+    def test_write_index(self):
+        pytest.importorskip("pyarrow")
         df = pd.DataFrame({"A": [1, 2, 3]})
-        check_round_trip(df, engine)
+        check_round_trip(df, "pyarrow")
 
         indexes = [
             [2, 3, 4],
@@ -446,12 +439,12 @@ def test_write_index(self, engine, using_copy_on_write, request):
             df.index = index
             if isinstance(index, pd.DatetimeIndex):
                 df.index = df.index._with_freq(None)  # freq doesn't round-trip
-            check_round_trip(df, engine, check_names=check_names)
+            check_round_trip(df, "pyarrow")
 
         # index with meta-data
         df.index = [0, 1, 2]
         df.index.name = "foo"
-        check_round_trip(df, engine)
+        check_round_trip(df, "pyarrow")
 
     def test_write_multiindex(self, pa):
         # Not supported in fastparquet as of 0.1.3 or older pyarrow version
@@ -1256,23 +1249,6 @@ def test_error_on_using_partition_cols_and_partition_on(
                 partition_cols=partition_cols,
             )
 
-    @pytest.mark.skipif(using_copy_on_write(), reason="fastparquet writes into Index")
-    def test_empty_dataframe(self, fp):
-        # GH #27339
-        df = pd.DataFrame()
-        expected = df.copy()
-        check_round_trip(df, fp, expected=expected)
-
-    @pytest.mark.skipif(using_copy_on_write(), reason="fastparquet writes into Index")
-    def test_timezone_aware_index(self, fp, timezone_aware_date_list):
-        idx = 5 * [timezone_aware_date_list]
-
-        df = pd.DataFrame(index=idx, data={"index_as_col": idx})
-
-        expected = df.copy()
-        expected.index.name = "index"
-        check_round_trip(df, fp, expected=expected)
-
     def test_close_file_handle_on_read_error(self):
         with tm.ensure_clean("test.parquet") as path:
             pathlib.Path(path).write_bytes(b"breakit")
@@ -1361,10 +1337,3 @@ def test_invalid_dtype_backend(self, engine):
             df.to_parquet(path)
             with pytest.raises(ValueError, match=msg):
                 read_parquet(path, dtype_backend="numpy")
-
-    @pytest.mark.skipif(using_copy_on_write(), reason="fastparquet writes into Index")
-    def test_empty_columns(self, fp):
-        # GH 52034
-        df = pd.DataFrame(index=pd.Index(["a", "b", "c"], name="custom name"))
-        expected = pd.DataFrame(index=pd.Index(["a", "b", "c"], name="custom name"))
-        check_round_trip(df, fp, expected=expected)

pandas/tests/io/parser/common/test_file_buffer_url.py

@@ -36,26 +36,20 @@ def test_reindex(self, multiindex_dataframe_random_data):
         tm.assert_frame_equal(reindexed, expected)
 
     def test_reindex_preserve_levels(
-        self, multiindex_year_month_day_dataframe_random_data, using_copy_on_write
+        self, multiindex_year_month_day_dataframe_random_data
     ):
         ymd = multiindex_year_month_day_dataframe_random_data
 
         new_index = ymd.index[::10]
         chunk = ymd.reindex(new_index)
-        if using_copy_on_write:
-            assert chunk.index.is_(new_index)
-        else:
-            assert chunk.index is new_index
+        assert chunk.index.is_(new_index)
 
         chunk = ymd.loc[new_index]
         assert chunk.index.equals(new_index)
 
         ymdT = ymd.T
         chunk = ymdT.reindex(columns=new_index)
-        if using_copy_on_write:
-            assert chunk.columns.is_(new_index)
-        else:
-            assert chunk.columns is new_index
+        assert chunk.columns.is_(new_index)
 
         chunk = ymdT.loc[:, new_index]
         assert chunk.columns.equals(new_index)