diff --git a/pandas/conftest.py b/pandas/conftest.py
index 003474b57c8e1..d17468d7ca67f 100644
--- a/pandas/conftest.py
+++ b/pandas/conftest.py
@@ -1905,6 +1905,7 @@ def warn_copy_on_write() -> bool:
     """
     Fixture to check if Copy-on-Write is enabled.
     """
+    pd.options.mode.copy_on_write = "warn"
     return (
         pd.options.mode.copy_on_write == "warn"
         and _get_option("mode.data_manager", silent=True) == "block"
diff --git a/pandas/tests/copy_view/test_indexing.py b/pandas/tests/copy_view/test_indexing.py
index 33b8ce218f029..6f3850ab64daa 100644
--- a/pandas/tests/copy_view/test_indexing.py
+++ b/pandas/tests/copy_view/test_indexing.py
@@ -1145,13 +1145,12 @@ def test_set_value_copy_only_necessary_column(
     view = df[:]
 
     if val == "a" and indexer[0] != slice(None):
-        # TODO(CoW-warn) assert the FutureWarning for CoW is also raised
         with tm.assert_produces_warning(
             FutureWarning, match="Setting an item of incompatible dtype is deprecated"
         ):
             indexer_func(df)[indexer] = val
     else:
-        with tm.assert_cow_warning(warn_copy_on_write):
+        with tm.assert_cow_warning(warn_copy_on_write and val == 100):
             indexer_func(df)[indexer] = val
 
     if using_copy_on_write: