Can't figure out how to test for "nothing" in the udev-test.pl script framework.
--- /dev/null
+#!/bin/bash
+
+RULES=ignore_test.rules
+CONFIG=ignore_test.conf
+
+export UDEV_TEST=yes
+export SYSFS_PATH=$PWD/sys/
+export UDEV_CONFIG_FILE=$PWD/$CONFIG
+
+cat > $RULES << EOF
+IGNORE, KERNEL="ttyUSB0"
+EOF
+
+cat > $CONFIG << EOF
+udev_root="$PWD/udev/"
+udev_db="$PWD/udev/.udev.tdb"
+udev_rules="$PWD/$RULES"
+udev_permissions="$PWD/udev.permissions"
+EOF
+
+mkdir udev
+
+export DEVPATH=class/tty/ttyUSB0
+export ACTION=add
+
+../udev tty
+ls -l udev
+
+export ACTION=remove
+../udev tty
+ls -l udev
+
+rm $RULES
+rm $CONFIG
+rm -rf udev