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diff --git a/Lib/test/autotest.py b/Lib/test/autotest.py
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+# Automatic Python regression test.
+#
+# Some essential parts of the Python interpreter are tested by the module
+# 'testall'.  (Despite its name, it doesn't test everything -- that would
+# be a truly Herculean task!)  When a test fails, 'testall' raises an
+# exception.  When all tests succeed, it produces quite a lot of output.
+#
+# For a normal regression test, this output is never looked at unless
+# something goes wrong.  Thus, it would be wise to suppress the output
+# normally.  This module does that, but it doesn't just throw the output
+# from 'testall' away -- it compares it with the output from a previous
+# run.  If a difference is noticed it raises an exception; if all is well,
+# it prints nothing except 'All tests OK.' at the very end.
+#
+# The output from a previous run is supposed to be in a file 'testall.out'
+# somewhere on the search path for modules (sys.path, initialized from
+# $PYTHONPATH plus some default places).
+#
+# Of course, if the normal output of the tests is changed because the
+# tests have been changed (rather than a test producing the wrong output),
+# 'autotest' will fail as well.  In this case, run 'testall' manually
+# and direct its output to 'testall.out'.
+#
+# The comparison uses (and demonstrates!) a rather new Python feature:
+# program output that normally goes to stdout (by 'print' statements
+# or by writing directly to sys.stdout) can be redirected to an
+# arbitrary class instance as long as it has a 'write' method.
+
+import os
+import sys
+
+# Function to find a file somewhere on sys.path
+def findfile(filename):
+	for dirname in sys.path:
+		fullname = os.path.join(dirname, filename)
+		if os.path.exists(fullname):
+			return fullname
+	return filename # Will cause exception later
+
+# Exception raised when the test failed (not the same as in test_support)
+TestFailed = 'autotest.TestFailed'
+
+# Class substituted for sys.stdout, to compare it with the given file
+class Compare:
+	def init(self, filename):
+		self.fp = open(filename, 'r')
+		return self
+	def write(self, data):
+		expected = self.fp.read(len(data))
+		if data <> expected:
+			raise TestFailed, \
+				'Writing: '+`data`+', expected: '+`expected`
+	def close(self):
+		self.fp.close()
+
+# The main program
+def main():
+	import sys
+	filename = findfile('testall.out')
+	real_stdout = sys.stdout
+	try:
+		sys.stdout = Compare().init(filename)
+		import testall
+	finally:
+		sys.stdout = real_stdout
+	print 'All tests OK.'
+
+main()