pt unit tests do dns lookup on "abcd"
Unplug your ethernet (but leave the interface up), and then run tor's 'make test'. It will stall at "pt/parsing" for a minute or so.
It has to do with these two tests in src/test/test_pt.c:
/* wrong addrport */
strcpy(line,"CMETHOD trebuchet socks4 abcd");
test_assert(parse_cmethod_line(line, mp) < 0);
[...]
/* wrong addr type */
strcpy(line,"SMETHOD trebuchet abcd");
test_assert(parse_smethod_line(line, mp) < 0);
parse_cmethod_line() calls tor_addr_port_lookup() which calls tor_addr_lookup() which triggers the dns lookup.
I haven't explored whether having my resolver answer the dns query can change the behavior of the unit tests.