'If C{showAttributes} has an item that is a 3-tuple, C{__str__} renders
the second item in the tuple as a key, and the contents of the
attribute named in the first item are rendered as the value. The value
is formatted using the third item in the tuple.'

def test_override(self):

    class Foo(util.FancyStrMixin, ):
        showAttributes = ('first', ('second', '2nd', '%.1f'))
        first = 1
        second = 2.111
    self.assertEqual(str(Foo()), '<Foo    first=1    2nd=2.1>')
