TEST-54-CREDS: add test cases for credential refreshing

test/integration-tests/TEST-54-CREDS/TEST-54-CREDS.units/refresh.sh

@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+# SPDX-License-Identifier: LGPL-2.1-or-later
+# shellcheck disable=SC2016
+set -eux
+set -o pipefail
+
+OUTPUT_FILE="$1"
+
+dump_creds_tree() {
+    grep . "$CREDENTIALS_DIRECTORY"/* >"$OUTPUT_FILE"
+}
+
+on_sighup() {
+    systemd-notify --reloading
+    dump_creds_tree
+    systemd-notify --ready
+}
+
+trap on_sighup SIGHUP
+
+export SYSTEMD_LOG_LEVEL=debug
+
+dump_creds_tree
+systemd-notify --ready
+
+sleep infinity &
+while :; do
+    wait || :
+done