Fix tests

Author: phofl

pandas/tests/extension/base/methods.py

@@ -249,14 +249,17 @@ def test_fillna_copy_frame(self, data_missing):
 
         assert df.A.values is not result.A.values
 
-    def test_fillna_copy_series(self, data_missing):
+    def test_fillna_copy_series(self, data_missing, no_op_with_cow: bool = False):
         arr = data_missing.take([1, 1])
         ser = pd.Series(arr)
 
         filled_val = ser[0]
         result = ser.fillna(filled_val)
 
-        assert ser._values is not result._values
+        if no_op_with_cow:
+            assert ser._values is result._values
+        else:
+            assert ser._values is not result._values
         assert ser._values is arr
 
     def test_fillna_length_mismatch(self, data_missing):

pandas/tests/extension/test_datetime.py

@@ -116,6 +116,11 @@ def test_combine_add(self, data_repeated):
         # Timestamp.__add__(Timestamp) not defined
         pass
 
+    def test_fillna_copy_series(self, data_missing, using_copy_on_write):
+        super().test_fillna_copy_series(
+            data_missing, no_op_with_cow=using_copy_on_write
+        )
+
 
 class TestInterface(BaseDatetimeTests, base.BaseInterfaceTests):
     pass

pandas/tests/extension/test_interval.py

@@ -132,6 +132,11 @@ def test_combine_add(self, data_repeated):
     def test_fillna_length_mismatch(self, data_missing):
         super().test_fillna_length_mismatch(data_missing)
 
+    def test_fillna_copy_series(self, data_missing, using_copy_on_write):
+        super().test_fillna_copy_series(
+            data_missing, no_op_with_cow=using_copy_on_write
+        )
+
 
 class TestMissing(BaseInterval, base.BaseMissingTests):
     # Index.fillna only accepts scalar `value`, so we have to xfail all

pandas/tests/extension/test_period.py

@@ -105,6 +105,11 @@ def test_diff(self, data, periods):
         else:
             super().test_diff(data, periods)
 
+    def test_fillna_copy_series(self, data_missing, using_copy_on_write):
+        super().test_fillna_copy_series(
+            data_missing, no_op_with_cow=using_copy_on_write
+        )
+
 
 class TestInterface(BasePeriodTests, base.BaseInterfaceTests):