tests: add check whether empty parameters are accepted by zipl

tests/zipl-empty-params/main.fmf

@@ -0,0 +1,17 @@
+summary: zipl-empty-params
+description: |
+    Check if zipl works with empty parameters in zipl.conf
+link: https://bugzilla.redhat.com/show_bug.cgi?id=2113884
+contact: Daniel Horák <dhorak@redhat.com>
+component:
+  - s390utils-core
+test: ./runtest.sh
+framework: beakerlib
+require:
+  - s390utils-core
+duration: 5m
+enabled: true
+adjust:
+  - when: arch != s390x
+    enabled: false
+    because: This test applies only to s390x systems.

tests/zipl-empty-params/runtest.sh

@@ -0,0 +1,56 @@
+#!/bin/bash
+# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+#
+#   Description: Check if zipl works with empty parameters in zipl.conf
+#   Author: Dan Horák <dhorak@redhat.com>
+#
+# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+#
+#   Copyright (c) 2025 Red Hat, Inc.
+#
+#   This program is free software: you can redistribute it and/or
+#   modify it under the terms of the GNU General Public License as
+#   published by the Free Software Foundation, either version 2 of
+#   the License, or (at your option) any later version.
+#
+#   This program is distributed in the hope that it will be
+#   useful, but WITHOUT ANY WARRANTY; without even the implied
+#   warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+#   PURPOSE.  See the GNU General Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License
+#   along with this program. If not, see http://www.gnu.org/licenses/.
+#
+# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+# Include Beaker environment
+. /usr/share/beakerlib/beakerlib.sh || exit 1
+
+PACKAGE="s390utils-core"
+
+rlJournalStart
+    rlPhaseStartSetup
+        rlAssertRpm $PACKAGE
+        rlRun "TmpDir=\$(mktemp -d)" 0 "Creating tmp directory"
+        rlRun "pushd $TmpDir"
+    rlPhaseEnd
+
+    rlPhaseStartTest "Check if zipl works with empty kernel parameter line"
+        [ -f /etc/zipl.conf ] && cp /etc/zipl.conf . || cp /usr/lib/s390-tools/zipl.conf .
+        version=$(uname -r)
+        cat >> ./zipl.conf << EOF
+
+[empty]
+target=/boot
+image=/boot/vmlinuz-$version
+ramdisk=/boot/initramfs-$version.img
+EOF
+        rlRun "zipl -V --dry-run -c ./zipl.conf"
+    rlPhaseEnd
+
+    rlPhaseStartCleanup
+        rlRun "popd"
+        rlRun "rm -r $TmpDir" 0 "Removing tmp directory"
+    rlPhaseEnd
+rlJournalPrintText
+rlJournalEnd