'Test the correctness of the coerce function.'

def test_file(self):

    arg = formmethod.File('name', allowNone=0)
    self.assertEqual(arg.coerce('something'), 'something')
    self.assertRaises(formmethod.InputError, arg.coerce, None)
    arg2 = formmethod.File('name')
    self.assertIsNone(arg2.coerce(None))
