[0/6] [0s]
[1/6] Fetching image [0s]
[2/6] Unpacking image [0s]
[3/6] Fetching kernel [0s]
[4/6] Fetching init image [0s]
[5/6] Unpacking init image [0s]
[6/6] Starting container [0s]
[6/6] Starting container [1s]
== extracted %post lua ==
local nl = '\n'
local cosh = '/usr/bin/cosh'
local f = io.open('/etc/shells', 'a+')
if f then
  f:seek('set')
  local shells = f:read('*all') or ''
  local normalized = nl..shells
  if shells ~= '' and shells:sub(-1) ~= nl then normalized = normalized..nl end
  if not normalized:find(nl..cosh..nl, 1, true) then
    local separator = (shells ~= '' and shells:sub(-1) ~= nl) and nl or ''
    f:write(separator, cosh, nl)
  end
  f:close()
end
== fixture (cat -A) ==
/bin/sh$
/bin/bash
rc_first=0
== after first run (cat -A) ==
/bin/sh$
/bin/bash$
/usr/bin/cosh$

rc_second=0
== after second run (cat -A) ==
/bin/sh$
/bin/bash$
/usr/bin/cosh$
glued_lines=0 standalone_entries=1
VERDICT: PASS (single clean entry, idempotent)
container_exit=0