tests/basics: Add test for set.difference_update with arg being itself.

dpgeorge · dpgeorge · commit 443cc0114d76 · 2016-09-28T11:10:27.000+10:00
diff --git a/tests/basics/set_difference.py b/tests/basics/set_difference.py
@@ -14,3 +14,6 @@
 print(sorted(s))
 print(s.difference_update({1}, [2]))
 print(sorted(s))
+
+s.difference_update(s)
+print(s)
