1co = coroutine.wrap(function()
2  co()
3end)
4
5local ok, msg = pcall(function()
6  co()
7end)
8assert(not ok and string.find(msg, "can not resume a running thread"))
9
10co = coroutine.wrap(function()
11  return 1
12end)
13assert(co() == 1)
14local ok, msg = pcall(function()
15  co()
16end)
17assert(not ok and string.find(msg, "can not resume a dead thread"))
18