def test_b(self):
filename = tempfile.mktemp()
s = FileStorage2(filename)
connection = Connection(s)
root = connection.get_root()
root['a'] = Persistent()
root['a'].b = 1
connection.commit()
root['b'] = Persistent()
connection.commit()
root['b'].a = root['a']
root['a'].b = 2
connection.commit()
root['a'].b = 3
connection.commit()
s.close()
hc = HistoryConnection(filename)
a = hc.get_root()['a']
assert len(hc.get_storage().index.history) == 6
hc.previous_instance(a)
assert a.b == 2
hc.previous_instance(a)
assert a.b == 1
hc.previous_instance(a)
assert not hasattr(a, '__dict__')
assert hc.get_root().keys() == []
hc.get_storage().fp.close()
os.unlink(filename)
