CLN: rollback unittest unralted to _item_cache

Author: chilin0525

pandas/tests/copy_view/test_indexing.py

@@ -734,6 +734,33 @@ def test_column_as_series_set_with_upcast(backend):
             s[0] = "foo"
 
 
+@pytest.mark.parametrize(
+    "method",
+    [
+        lambda df: df["a"],
+        lambda df: df.loc[:, "a"],
+        lambda df: df.iloc[:, 0],
+    ],
+    ids=["getitem", "loc", "iloc"],
+)
+def test_column_as_series_no_item_cache(request, backend, method):
+    # Case: selecting a single column (which now also uses Copy-on-Write to protect
+    # the view) should always give a new object (i.e. not make use of a cache)
+    dtype_backend, DataFrame, _ = backend
+    df = DataFrame({"a": [1, 2, 3], "b": [4, 5, 6], "c": [0.1, 0.2, 0.3]})
+    df_orig = df.copy()
+
+    s1 = method(df)
+    s2 = method(df)
+
+    assert s1 is not s2
+
+    s1.iloc[0] = 0
+
+    tm.assert_series_equal(s2, df_orig["a"])
+    tm.assert_frame_equal(df, df_orig)
+
+
 # TODO add tests for other indexing methods on the Series