SF patch #736962:  Port tests to unittest
(Contributed by Walter Dörwald).

* Convert three test modules to unittest format.
* Expanded coverage in test_structseq.py.
* Raymond added a new test in test_sets.py
diff --git a/Lib/test/test_sets.py b/Lib/test/test_sets.py
index f0a1925..416b7ca 100644
--- a/Lib/test/test_sets.py
+++ b/Lib/test/test_sets.py
@@ -596,6 +596,7 @@
             self.set.difference(self.other)
         else:
             self.assertRaises(TypeError, self.set.difference, self.other)
+
 #------------------------------------------------------------------------------
 
 class TestOnlySetsNumeric(TestOnlySetsInBinaryOps):
@@ -647,6 +648,14 @@
         self.other = gen()
         self.otherIsIterable = True
 
+#------------------------------------------------------------------------------
+
+class TestOnlySetsofSets(TestOnlySetsInBinaryOps):
+    def setUp(self):
+        self.set   = Set((1, 2, 3))
+        self.other = [Set('ab'), ImmutableSet('cd')]
+        self.otherIsIterable = True
+
 #==============================================================================
 
 class TestCopying(unittest.TestCase):
@@ -801,6 +810,7 @@
         TestOnlySetsTuple,
         TestOnlySetsString,
         TestOnlySetsGenerator,
+        TestOnlySetsofSets,
         TestCopyingEmpty,
         TestCopyingSingleton,
         TestCopyingTriple,