The usual

Lib/dos-8x3/test_pop.py

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+#! /usr/bin/env python
+"""Test script for popen2.py
+   Christian Tismer
+"""
+
+# popen2 contains its own testing routine
+# which is especially useful to see if open files
+# like stdin can be read successfully by a forked 
+# subprocess.
+
+def main():
+    from os import fork # skips test through ImportError
+    import popen2
+    popen2._test()
+
+main()
+