From 43be6b747e0960e3bf41163cbccaabb48737143b Mon Sep 17 00:00:00 2001
From: Aniket Singh Yadav <singhyadavaniket43@gmail.com>
Date: Sun, 16 Nov 2025 21:36:34 +0530
Subject: [PATCH 1/3] EA attribute specifying whether copy=False is ignored

---
 pandas/tests/extension/base/missing.py | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/pandas/tests/extension/base/missing.py b/pandas/tests/extension/base/missing.py
index cee565d4f7c1e..3a149025421b2 100644
--- a/pandas/tests/extension/base/missing.py
+++ b/pandas/tests/extension/base/missing.py
@@ -6,6 +6,8 @@
 
 
 class BaseMissingTests:
+    _supports_fillna_copy_false = True
+
     def test_isna(self, data_missing):
         expected = np.array([True, False])
 
@@ -179,3 +181,9 @@ def test_fillna_fill_other(self, data):
         expected = pd.DataFrame({"A": data, "B": [0.0] * len(result)})
 
         tm.assert_frame_equal(result, expected)
+
+    def test_fillna_readonly(self, data_missing):
+        fill_value = data_missing[1]
+        result = data_missing.fillna(fill_value, copy=False)
+        expected = data_missing.fillna(fill_value, copy=True)
+        tm.assert_extension_array_equal(result, expected)

From 251ff22a05eaf4b706095b9f2593d18dadf146d4 Mon Sep 17 00:00:00 2001
From: Aniket Singh Yadav <singhyadavaniket43@gmail.com>
Date: Tue, 18 Nov 2025 01:48:46 +0530
Subject: [PATCH 2/3] EA attribute specifying whether copy=False is ignored

---
 pandas/tests/extension/test_numpy.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/pandas/tests/extension/test_numpy.py b/pandas/tests/extension/test_numpy.py
index 691ce9341b788..e19d1d7471ea6 100644
--- a/pandas/tests/extension/test_numpy.py
+++ b/pandas/tests/extension/test_numpy.py
@@ -167,6 +167,8 @@ def skip_numpy_object(dtype, request):
 
 
 class TestNumpyExtensionArray(base.ExtensionTests):
+    _supports_fillna_copy_false = False
+
     @pytest.mark.skip(reason="We don't register our dtype")
     # We don't want to register. This test should probably be split in two.
     def test_from_dtype(self, data):

From 0df38dbe0da71715d562e07797be50a452a92852 Mon Sep 17 00:00:00 2001
From: Aniket Singh Yadav <singhyadavaniket43@gmail.com>
Date: Thu, 20 Nov 2025 19:04:46 +0530
Subject: [PATCH 3/3] EA attribute specifying whether copy=False is ignored

---
 pandas/tests/extension/test_sparse.py | 15 ---------------
 1 file changed, 15 deletions(-)

diff --git a/pandas/tests/extension/test_sparse.py b/pandas/tests/extension/test_sparse.py
index 4cbbda990b294..72f9a13910cc2 100644
--- a/pandas/tests/extension/test_sparse.py
+++ b/pandas/tests/extension/test_sparse.py
@@ -237,21 +237,6 @@ def test_isna(self, data_missing):
     def test_fillna_no_op_returns_copy(self, data, request):
         super().test_fillna_no_op_returns_copy(data)
 
-    def test_fillna_readonly(self, data_missing):
-        # copy keyword is ignored by SparseArray.fillna
-        # -> copy=True vs False doesn't make a difference
-        data = data_missing.copy()
-        data._readonly = True
-
-        result = data.fillna(data_missing[1])
-        assert result[0] == data_missing[1]
-        tm.assert_extension_array_equal(data, data_missing)
-
-        # fillna(copy=False) is ignored -> so same result as above
-        result = data.fillna(data_missing[1], copy=False)
-        assert result[0] == data_missing[1]
-        tm.assert_extension_array_equal(data, data_missing)
-
     @pytest.mark.xfail(reason="Unsupported")
     def test_fillna_series(self, data_missing):
         # this one looks doable.