#11763: don't use difflib in TestCase.assertMultiLineEqual if the strings are too long.
diff --git a/Lib/unittest/case.py b/Lib/unittest/case.py
index ecb6a3e..dcaae93 100644
--- a/Lib/unittest/case.py
+++ b/Lib/unittest/case.py
@@ -169,6 +169,10 @@
maxDiff = 80*8
+ # If a string is longer than _diffThreshold, use normal comparison instead
+ # of difflib. See #11763.
+ _diffThreshold = 2**16
+
# Attribute used by TestSuite for classSetUp
_classSetupFailed = False
@@ -900,6 +904,10 @@
'Second argument is not a string')
if first != second:
+ # don't use difflib if the strings are too long
+ if (len(first) > self._diffThreshold or
+ len(second) > self._diffThreshold):
+ self._baseAssertEqual(first, second, msg)
firstlines = first.splitlines(True)
secondlines = second.splitlines(True)
if len(firstlines) == 1 and first.strip('\r\n') == first: