diff --git a/test/units/TEST-07-PID1.concurrency.sh b/test/units/TEST-07-PID1.concurrency.sh
new file mode 100755
index 0000000000..0959c22541
--- /dev/null
+++ b/test/units/TEST-07-PID1.concurrency.sh
@@ -0,0 +1,128 @@
+#!/usr/bin/env bash
+# SPDX-License-Identifier: LGPL-2.1-or-later
+# shellcheck disable=SC2016
+set -eux
+set -o pipefail
+
+# shellcheck source=test/units/test-control.sh
+. "$(dirname "$0")"/test-control.sh
+# shellcheck source=test/units/util.sh
+. "$(dirname "$0")"/util.sh
+
+cat >/etc/systemd/system/concurrency1.slice <<EOF
+[Slice]
+ConcurrencyHardMax=4
+ConcurrencySoftMax=3
+EOF
+
+cat >/etc/systemd/system/sleepforever1@.service <<EOF
+[Service]
+Slice=concurrency1.slice
+ExecStart=sleep infinity
+EOF
+
+cat >/etc/systemd/system/sync-on-sleepforever1@.service <<EOF
+[Unit]
+After=sleepforever1@%i.service
+
+[Service]
+ExecStart=true
+EOF
+
+cat >/etc/systemd/system/concurrency1-concurrency2.slice <<EOF
+[Slice]
+ConcurrencySoftMax=1
+EOF
+
+cat >/etc/systemd/system/sleepforever2@.service <<EOF
+[Service]
+Slice=concurrency1-concurrency2.slice
+ExecStart=sleep infinity
+EOF
+cat >/etc/systemd/system/concurrency1-concurrency3.slice <<EOF
+[Slice]
+ConcurrencySoftMax=1
+EOF
+
+cat >/etc/systemd/system/sleepforever3@.service <<EOF
+[Service]
+Slice=concurrency1-concurrency3.slice
+ExecStart=sleep infinity
+EOF
+
+systemctl daemon-reload
+
+systemctl status concurrency1.slice ||:
+(! systemctl is-active concurrency1.slice)
+systemctl start sleepforever1@a.service
+systemctl is-active concurrency1.slice
+systemctl status concurrency1.slice
+systemctl show concurrency1.slice
+systemctl start sleepforever1@b.service
+systemctl status concurrency1.slice
+systemctl start sleepforever1@c.service
+systemctl status concurrency1.slice
+
+# The fourth call should hang because the soft limit is hit, verify that
+timeout 1s systemctl start sleepforever1@d.service && test "$?" -eq 124
+systemctl status concurrency1.slice
+systemctl list-jobs
+
+systemctl is-active sleepforever1@a.service
+systemctl is-active sleepforever1@b.service
+systemctl is-active sleepforever1@c.service
+(! systemctl is-active sleepforever1@d.service)
+systemctl status concurrency1.slice
+
+# Now stop one, which should trigger the queued unit immediately
+systemctl stop sleepforever1@b.service
+
+# the 'd' instance should still be queued, now sync on it via another unit (which doesn't pull it in again, but is ordered after it)
+systemctl start sync-on-sleepforever1@d.service
+
+systemctl is-active sleepforever1@a.service
+(! systemctl is-active sleepforever1@b.service)
+systemctl is-active sleepforever1@c.service
+systemctl is-active sleepforever1@d.service
+
+# A fifth one should immediately fail because of the hard limit once we re-enqueue the fourth
+systemctl --no-block start sleepforever1@b.service
+(! systemctl start sleepforever1@e.service)
+
+systemctl stop sleepforever1@b.service
+systemctl stop sleepforever1@c.service
+systemctl stop sleepforever1@d.service
+
+# Now go for some nesting
+systemctl start sleepforever2@a.service
+systemctl is-active sleepforever2@a.service
+systemctl is-active concurrency1-concurrency2.slice
+systemctl status concurrency1.slice
+systemctl status concurrency1-concurrency2.slice
+
+# This service is in a sibling slice. Should be delayed
+timeout 1s systemctl start sleepforever3@a.service && test "$?" -eq 124
+
+# And the hard limit should make the next job completely fail
+(! systemctl start sleepforever3@b.service)
+
+# Stopping one service should not suffice to make the service run, because we need two slots: for slice and service
+systemctl stop sleepforever2@a.service
+timeout 1s systemctl start sleepforever3@a.service && test "$?" -eq 124
+
+# Stopping one more slice should be enough though
+systemctl stop concurrency1-concurrency2.slice
+systemctl start sleepforever3@a.service
+
+systemctl stop concurrency1.slice
+systemctl reset-failed
+
+rm /etc/systemd/system/concurrency1.slice
+rm /etc/systemd/system/concurrency1-concurrency2.slice
+rm /etc/systemd/system/concurrency1-concurrency3.slice
+rm /etc/systemd/system/sleepforever1@.service
+rm /etc/systemd/system/sync-on-sleepforever1@.service
+rm /etc/systemd/system/sleepforever2@.service
+rm /etc/systemd/system/sleepforever3@.service
+
+systemctl daemon-reload