diff --git a/test/units/testsuite-17.link-property.sh b/test/units/testsuite-17.link-property.sh
new file mode 100755
index 0000000000..a43ad22b43
--- /dev/null
+++ b/test/units/testsuite-17.link-property.sh
@@ -0,0 +1,201 @@
+#!/usr/bin/env bash
+# SPDX-License-Identifier: LGPL-2.1-or-later
+set -ex
+set -o pipefail
+
+# shellcheck source=test/units/util.sh
+. "$(dirname "$0")"/util.sh
+
+udevadm control --log-level=debug
+
+mkdir -p /run/systemd/network/
+cat >/run/systemd/network/10-test.link <<EOF
+[Match]
+Kind=dummy
+MACAddress=00:50:56:c0:00:19
+
+[Link]
+Name=test1
+EOF
+
+mkdir /run/systemd/network/10-test.link.d
+cat >/run/systemd/network/10-test.link.d/10-override.conf <<EOF
+[Link]
+Property=HOGE=foo BAR=baz SHOULD_BE_UNSET=unset
+UnsetProperty=SHOULD_BE_UNSET
+EOF
+
+udevadm control --reload
+
+ip link add address 00:50:56:c0:00:19 type dummy
+udevadm wait --settle --timeout=30 /sys/class/net/test1
+output=$(udevadm info --query property /sys/class/net/test1)
+assert_in "HOGE=foo" "$output"
+assert_in "BAR=baz" "$output"
+assert_not_in "SHOULD_BE_UNSET=" "$output"
+assert_in "ID_NET_LINK_FILE=/run/systemd/network/10-test.link" "$output"
+assert_in "ID_NET_LINK_FILE_DROPINS=/run/systemd/network/10-test.link.d/10-override.conf" "$output"
+assert_in "ID_NET_NAME=test1" "$output"
+
+cat >/run/systemd/network/10-test.link.d/11-override.conf <<EOF
+[Link]
+Property=
+Property=HOGE2=foo2 BAR2=baz2 SHOULD_BE_UNSET=unset
+ImportProperty=HOGE
+EOF
+
+udevadm control --reload
+
+udevadm trigger --settle --action add /sys/class/net/test1
+output=$(udevadm info --query property /sys/class/net/test1)
+assert_in "HOGE=foo" "$output"
+assert_in "HOGE2=foo2" "$output"
+assert_not_in "BAR=" "$output"
+assert_in "BAR2=baz2" "$output"
+assert_not_in "SHOULD_BE_UNSET=" "$output"
+assert_in "ID_NET_LINK_FILE=/run/systemd/network/10-test.link" "$output"
+assert_in "ID_NET_LINK_FILE_DROPINS=/run/systemd/network/10-test.link.d/10-override.conf:/run/systemd/network/10-test.link.d/11-override.conf" "$output"
+assert_in "ID_NET_NAME=test1" "$output"
+
+# On change event, .link file will not be applied.
+udevadm trigger --settle --action change /sys/class/net/test1
+output=$(udevadm info --query property /sys/class/net/test1)
+assert_not_in "HOGE=" "$output"
+assert_not_in "HOGE2=" "$output"
+assert_not_in "BAR=" "$output"
+assert_not_in "BAR2=" "$output"
+assert_not_in "SHOULD_BE_UNSET=" "$output"
+assert_in "ID_NET_LINK_FILE=/run/systemd/network/10-test.link" "$output"
+assert_in "ID_NET_LINK_FILE_DROPINS=/run/systemd/network/10-test.link.d/10-override.conf:/run/systemd/network/10-test.link.d/11-override.conf" "$output"
+assert_in "ID_NET_NAME=test1" "$output"
+
+### testing with udevadm test-builtin
+output=$(udevadm test-builtin --action add net_setup_link /sys/class/net/test1)
+assert_not_in "HOGE=" "$output"
+assert_in "HOGE2=foo2" "$output"
+assert_not_in "BAR=" "$output"
+assert_in "BAR2=baz2" "$output"
+assert_in "SHOULD_BE_UNSET=" "$output"  # this is expected, as an empty assignment is also logged.
+assert_in "ID_NET_LINK_FILE=/run/systemd/network/10-test.link" "$output"
+assert_in "ID_NET_LINK_FILE_DROPINS=/run/systemd/network/10-test.link.d/10-override.conf:/run/systemd/network/10-test.link.d/11-override.conf" "$output"
+assert_in "ID_NET_NAME=test1" "$output"
+
+# check that test-builtin command does not update udev database.
+output=$(udevadm info --query property /sys/class/net/test1)
+assert_not_in "HOGE=" "$output"
+assert_not_in "HOGE2=" "$output"
+assert_not_in "BAR=" "$output"
+assert_not_in "BAR2=" "$output"
+assert_not_in "SHOULD_BE_UNSET=" "$output"
+assert_in "ID_NET_LINK_FILE=/run/systemd/network/10-test.link" "$output"
+assert_in "ID_NET_LINK_FILE_DROPINS=/run/systemd/network/10-test.link.d/10-override.conf:/run/systemd/network/10-test.link.d/11-override.conf" "$output"
+assert_in "ID_NET_NAME=test1" "$output"
+
+output=$(udevadm test-builtin --action change net_setup_link /sys/class/net/test1)
+assert_not_in "HOGE=" "$output"
+assert_not_in "HOGE2=" "$output"
+assert_not_in "BAR=" "$output"
+assert_not_in "BAR2=" "$output"
+assert_not_in "SHOULD_BE_UNSET=" "$output"
+assert_in "ID_NET_LINK_FILE=/run/systemd/network/10-test.link" "$output"
+assert_in "ID_NET_LINK_FILE_DROPINS=/run/systemd/network/10-test.link.d/10-override.conf:/run/systemd/network/10-test.link.d/11-override.conf" "$output"
+assert_in "ID_NET_NAME=test1" "$output"
+
+output=$(udevadm info --query property /sys/class/net/test1)
+assert_not_in "HOGE=" "$output"
+assert_not_in "HOGE2=" "$output"
+assert_not_in "BAR=" "$output"
+assert_not_in "BAR2=" "$output"
+assert_not_in "SHOULD_BE_UNSET=" "$output"
+assert_in "ID_NET_LINK_FILE=/run/systemd/network/10-test.link" "$output"
+assert_in "ID_NET_LINK_FILE_DROPINS=/run/systemd/network/10-test.link.d/10-override.conf:/run/systemd/network/10-test.link.d/11-override.conf" "$output"
+assert_in "ID_NET_NAME=test1" "$output"
+
+### testing with udevadm test
+output=$(udevadm test --action add /sys/class/net/test1)
+assert_not_in "HOGE=" "$output"
+assert_in "HOGE2=foo2" "$output"
+assert_not_in "BAR=" "$output"
+assert_in "BAR2=baz2" "$output"
+assert_not_in "SHOULD_BE_UNSET=" "$output"
+assert_in "ID_NET_LINK_FILE=/run/systemd/network/10-test.link" "$output"
+assert_in "ID_NET_LINK_FILE_DROPINS=/run/systemd/network/10-test.link.d/10-override.conf:/run/systemd/network/10-test.link.d/11-override.conf" "$output"
+assert_in "ID_NET_NAME=test1" "$output"
+
+# check that test command _does_ update udev database.
+output=$(udevadm info --query property /sys/class/net/test1)
+assert_not_in "HOGE=" "$output"
+assert_in "HOGE2=foo2" "$output"
+assert_not_in "BAR=" "$output"
+assert_in "BAR2=baz2" "$output"
+assert_not_in "SHOULD_BE_UNSET=" "$output"
+assert_in "ID_NET_LINK_FILE=/run/systemd/network/10-test.link" "$output"
+assert_in "ID_NET_LINK_FILE_DROPINS=/run/systemd/network/10-test.link.d/10-override.conf:/run/systemd/network/10-test.link.d/11-override.conf" "$output"
+assert_in "ID_NET_NAME=test1" "$output"
+
+output=$(udevadm test --action change /sys/class/net/test1)
+assert_not_in "HOGE=" "$output"
+assert_not_in "HOGE2=" "$output"
+assert_not_in "BAR=" "$output"
+assert_not_in "BAR2=" "$output"
+assert_not_in "SHOULD_BE_UNSET=" "$output"
+assert_in "ID_NET_LINK_FILE=/run/systemd/network/10-test.link" "$output"
+assert_in "ID_NET_LINK_FILE_DROPINS=/run/systemd/network/10-test.link.d/10-override.conf:/run/systemd/network/10-test.link.d/11-override.conf" "$output"
+assert_in "ID_NET_NAME=test1" "$output"
+
+output=$(udevadm info --query property /sys/class/net/test1)
+assert_not_in "HOGE=" "$output"
+assert_not_in "HOGE2=" "$output"
+assert_not_in "BAR=" "$output"
+assert_not_in "BAR2=" "$output"
+assert_not_in "SHOULD_BE_UNSET=" "$output"
+assert_in "ID_NET_LINK_FILE=/run/systemd/network/10-test.link" "$output"
+assert_in "ID_NET_LINK_FILE_DROPINS=/run/systemd/network/10-test.link.d/10-override.conf:/run/systemd/network/10-test.link.d/11-override.conf" "$output"
+assert_in "ID_NET_NAME=test1" "$output"
+
+# test for specifiers
+cat >/run/systemd/network/10-test.link.d/12-override.conf <<EOF
+[Link]
+Property=
+Property=LINK_VERSION=%v
+EOF
+
+udevadm control --reload
+
+output=$(udevadm test --action add /sys/class/net/test1)
+assert_in "LINK_VERSION=$(uname -r)" "$output"
+
+output=$(udevadm info --query property /sys/class/net/test1)
+assert_in "LINK_VERSION=$(uname -r)" "$output"
+
+# test for constant properties
+cat >/run/systemd/network/10-test.link.d/13-override.conf <<EOF
+[Link]
+Property=
+Property=ACTION=foo IFINDEX=bar
+UnsetProperty=DEVPATH
+EOF
+
+udevadm control --reload
+
+output=$(udevadm test --action add /sys/class/net/test1)
+assert_in "ACTION=add" "$output"
+assert_not_in "ACTION=foo" "$output"
+assert_in "IFINDEX=" "$output"
+assert_not_in "IFINDEX=bar" "$output"
+assert_in "DEVPATH=" "$output"
+
+output=$(udevadm info --query property /sys/class/net/test1)
+assert_not_in "ACTION=foo" "$output"
+assert_in "IFINDEX=" "$output"
+assert_not_in "IFINDEX=bar" "$output"
+assert_in "DEVPATH=" "$output"
+
+# cleanup
+ip link del dev test1
+
+rm -f /run/systemd/network/10-test.link
+rm -rf /run/systemd/network/10-test.link.d
+udevadm control --reload --log-level=info
+
+exit 0