test: introduce TEST-09-REBOOT

To test stuff involving state preserved across (multiple) reboots, like
journal boot IDs.

test/units/util.sh

@@ -3,6 +3,9 @@
 
 # Utility functions for shell tests
 
+# shellcheck disable=SC2034
+[[ -e /var/tmp/.systemd_reboot_count ]] && REBOOT_COUNT="$(</var/tmp/.systemd_reboot_count)" || REBOOT_COUNT=0
+
 assert_true() {(
     set +ex
 
@@ -16,7 +19,6 @@ assert_true() {(
     fi
 )}
 
-
 assert_eq() {(
     set +ex
 
@@ -57,6 +59,11 @@ assert_rc() {(
     assert_eq "$rc" "$exp"
 )}
 
+assert_not_reached() {
+    echo >&2 "Code should not be reached at ${BASH_SOURCE[1]}:${BASH_LINENO[1]}, function ${FUNCNAME[1]}()"
+    exit 1
+}
+
 run_and_grep() {(
     set +ex
 
@@ -149,3 +156,18 @@ create_dummy_container() {
     cp -a /testsuite-13-container-template/* "$root"
     coverage_create_nspawn_dropin "$root"
 }
+
+# Bump the reboot counter and call systemctl with the given arguments
+systemctl_final() {
+    local counter
+
+    if [[ $# -eq 0 ]]; then
+        echo >&2 "Missing arguments"
+        exit 1
+    fi
+
+    [[ -e /var/tmp/.systemd_reboot_count ]] && counter="$(</var/tmp/.systemd_reboot_count)" || counter=0
+    echo "$((counter + 1))" >/var/tmp/.systemd_reboot_count
+
+    systemctl "$@"
+}