This is overkill for the current code path, but should provide some
robustness for future changes in error handling.
gdb --batch-silent --return-child-result -x index-file-$code.gdb \
--args notmuch insert < $gen_msg_filename
test_expect_equal $? 1
+
+test_begin_subtest "success exit with --keep when add_message returns $code"
+gdb --batch-silent --return-child-result -x index-file-$code.gdb \
+ --args notmuch insert --keep < $gen_msg_filename
+test_expect_equal $? 0
done
test_done