formerly this module tested only to_string(), so a bug in parser() of 'TimeExceeded' was overlooked.
this patch will bring the module to test all the methods of all the classes in 'icmp' module.
Signed-off-by: itoyuichi <ito.yuichi0@gmail.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>