diff --git a/pandas/_testing/__init__.py b/pandas/_testing/__init__.py
index a89946d1f8cc8..5919b27d2f4e9 100644
--- a/pandas/_testing/__init__.py
+++ b/pandas/_testing/__init__.py
@@ -1083,8 +1083,10 @@ def shares_memory(left, right) -> bool:
     if isinstance(left, ExtensionArray) and left.dtype == "string[pyarrow]":
         # https://github.com/pandas-dev/pandas/pull/43930#discussion_r736862669
         if isinstance(right, ExtensionArray) and right.dtype == "string[pyarrow]":
-            left_pa_data = left._data
-            right_pa_data = right._data
+            # for mypy
+            left_pa_data = getattr(left, "_data")
+            right_pa_data = getattr(right, "_data")
+            assert right_pa_data is not None and left_pa_data is not None
             left_buf1 = left_pa_data.chunk(0).buffers()[1]
             right_buf1 = right_pa_data.chunk(0).buffers()[1]
             return left_buf1 == right_buf1