ENH: Add tests for set and frozenset pretty-printing.

IPython/lib/tests/test_pretty.py

@@ -84,6 +84,20 b' def test_callability_checking():'
 
     nt.assert_equal(gotoutput, expectedoutput)
 
+
+def test_sets():
+    """
+    Test that set and frozenset use Python 3 formatting.
+    """
+    objects = [set(), frozenset(), set([1]), frozenset([1]), set([1,2]),
+        frozenset([1,2])]
+    expected = ['set()', 'frozenset()', '{1}', 'frozenset({1})', '{1, 2}',
+        'frozenset({1, 2})']
+    for obj, expected_output in zip(objects, expected):
+        got_output = pretty.pretty(obj)
+        yield nt.assert_equal, got_output, expected_output
+
+
 @skip_without('xxlimited')
 def test_pprint_heap_allocated_type():
     """