specify posix.stdio:

- before:

    stdio = require "posix.stdio"

- describe fdopen:

    - before:

        fdopen = stdio.fdopen

        unistd = require "posix.unistd"

        STDOUT_FILENO = unistd.STDOUT_FILENO

        f = fdopen (STDOUT_FILENO, "w")

    - context with bad arguments:

        badargs.diagnose (fdopen, "(int,string)")

    - it duplicates a stream:

        expect (type (f)).to_be "userdata"

    - it writes to the duplicated stream:

        -- Lua 5.1 file.write returns true; > 5.1 returns file handle

        expect (f:write ("writing to fdopen(stdout)\n")).not_to_be (nil)