diff -r 0e8836be9541 -r ad8389ecd3f5 mercurial/testing/storage.py
--- a/mercurial/testing/storage.py	Fri Sep 28 11:03:17 2018 -0700
+++ b/mercurial/testing/storage.py	Fri Sep 28 11:16:44 2018 -0700
@@ -199,13 +199,13 @@
         with self.assertRaises(error.LookupError):
             f.lookup(hex(node)[0:12])
 
-        with self.assertRaises(IndexError):
+        with self.assertRaises(error.LookupError):
             f.lookup(-2)
 
         with self.assertRaises(error.LookupError):
             f.lookup(b'-2')
 
-        with self.assertRaises(IndexError):
+        with self.assertRaises(error.LookupError):
             f.lookup(1)
 
         with self.assertRaises(error.LookupError):