[miky@gremlin ~]$ bash -version
GNU bash, version 4.3.8(1)-release (x86_64-unknown-linux-gnu)
Copyright (C) 2013 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
[miky@gremlin ~]$ builtin test \( ! ! \)
bash: test: `)' expected
[miky@gremlin ~]$ echo $?
2
[miky@gremlin ~]$


The bug is in term() function in test.c: the argv[pos] is not tested for ")" in top-level but only in the if ( "(" ) {} branch. The last top-level test "consumes" the last argument before it returns back to the original call origin within the if ( "(" ) {} branch.

Not a C developer, hence no patch. Sorry.