from unittest import TestCase import simplejson as json class JSONTestObject: pass class RecursiveJSONEncoder(json.JSONEncoder): recurse = False def default(self, o): if o is JSONTestObject: if self.recurse: return [JSONTestObject] else: return 'JSONTestObject' return json.JSONEncoder.default(o) class TestRecursion(TestCase): def test_listrecursion(self): x = [] x.append(x) try: json.dumps(x) except ValueError: pass else: self.fail("didn't raise ValueError on list recursion") x = [] y = [x] x.append(y) try: json.dumps(x) except ValueError: pass else: self.fail("didn't raise ValueError on alternating list recursion") y = [] x = [y, y] # ensure that the marker is cleared json.dumps(x) def test_dictrecursion(self): x = {} x["test"] = x try: json.dumps(x) except ValueError: pass else: self.fail("didn't raise ValueError on dict recursion") x = {} y = {"a": x, "b": x} # ensure that the marker is cleared json.dumps(y) def test_defaultrecursion(self): enc = RecursiveJSONEncoder() self.assertEqual(enc.encode(JSONTestObject), '"JSONTestObject"') enc.recurse = True try: enc.encode(JSONTestObject) except ValueError: pass else: self.fail("didn't raise ValueError on default recursion")