Fix check_untyped_defs errors in capture

1 files changed, 4 insertions, 2 deletions

diff --git a/testing/test_capture.py b/testing/test_capture.py
index 0f7db4b8e..180637db6 100644
--- a/testing/test_capture.py
+++ b/testing/test_capture.py
@@ -6,6 +6,8 @@ import subprocess
 import sys
 import textwrap
 from io import UnsupportedOperation
+from typing import List
+from typing import TextIO
 
 import py
 
@@ -857,8 +859,8 @@ def tmpfile(testdir):
 
 
 @needsosdup
-def test_dupfile(tmpfile):
-    flist = []
+def test_dupfile(tmpfile) -> None:
+    flist = []  # type: List[TextIO]
     for i in range(5):
         nf = capture.safe_text_dupfile(tmpfile, "wb")
         assert nf != tmpfile