StringIO.StringIO -> io.StringIO (closes #17168)
diff --git a/Doc/library/test.rst b/Doc/library/test.rst
index 2e8ba32..940d3e7 100644
--- a/Doc/library/test.rst
+++ b/Doc/library/test.rst
@@ -364,9 +364,9 @@
.. function:: captured_stdout()
- A context manager that runs the :keyword:`with` statement body using
- a :class:`StringIO.StringIO` object as sys.stdout. That object can be
- retrieved using the ``as`` clause of the :keyword:`with` statement.
+ A context manager that runs the :keyword:`with` statement body using a
+ :class:`io.StringIO` object as sys.stdout. That object can be retrieved
+ using the ``as`` clause of the :keyword:`with` statement.
Example use::