TEST-04-JOURNAL: add test case for log filtering through syslog

For issue #38361.

test/integration-tests/TEST-04-JOURNAL/TEST-04-JOURNAL.units/logs-filtering-syslog.py

@@ -0,0 +1,14 @@
+#!/usr/bin/python3
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+import subprocess
+import syslog
+
+if __name__ == '__main__':
+    syslog.openlog(ident="logs-filtering", logoption=syslog.LOG_PID)
+    syslog.syslog(syslog.LOG_NOTICE, "Logging from the service, and ~more~ foo bar")
+
+    subprocess.check_output(
+        ['journalctl', '--sync'],
+        stdin=subprocess.DEVNULL,
+        text=True)

test/integration-tests/TEST-04-JOURNAL/TEST-04-JOURNAL.units/logs-filtering-syslog.service

@@ -0,0 +1,8 @@
+[Unit]
+Description=Log filtering unit
+
+[Service]
+Type=oneshot
+ExecStart=/usr/lib/systemd/tests/testdata/TEST-04-JOURNAL.units/logs-filtering-syslog.py
+SyslogLevel=notice
+LogLevelMax=info

test/units/TEST-04-JOURNAL.LogFilterPatterns.sh

@@ -119,6 +119,7 @@ test_delegate() {
 }
 
 test_service logs-filtering.service
+test_service logs-filtering-syslog.service
 test_delegate delegated-cgroup-filtering.service
 
 systemctl log-level "$SAVED_LOG_LEVEL"