new_contents: """ Test list packing and unpacking. """
  
  import xcffib
  import struct
  
  class TestList(object):
  
      def test_struct_pack_uses_List(self):
          # suppose we have a list of ints...
          ints = struct.pack("=IIII", *range(4))
  
          # Unpacker wants a cffi.cdata
          cffi_ints = xcffib.bytes_to_cdata(ints)
  
          l = xcffib.List(xcffib.Unpacker(cffi_ints), "I", count=4)
          ints2 = struct.pack("=IIII", *l)
  
          # after packing and unpacking, we should still have those ints
          assert ints == ints2
  
subject: Test that list packing is idempotent