Add Sanity/default-java test

tests/Sanity/default-java/main.fmf

@@ -0,0 +1,6 @@
+summary: javapackages-tools default Java test
+description: |
+  Test which Java is used as default Java for running applications.
+  Covers: https://fedoraproject.org/wiki/Changes/Java21
+require:
+  - javapackages-tools

tests/Sanity/default-java/runtest.sh

@@ -0,0 +1,21 @@
+#!/bin/bash
+# Author: Mikolaj Izdebski <mizdebsk@redhat.com>
+. /usr/share/beakerlib/beakerlib.sh
+
+rlJournalStart
+
+  rlPhaseStartTest
+    rlAssertRpm javapackages-tools
+    rlAssertExists /usr/share/java-utils/java-functions javapackages-tools
+    unset JAVA_HOME
+    export _prefer_jre=true
+    rlRun -s ". /usr/share/java-utils/java-functions && set_jvm && echo JAVA_HOME is \$JAVA_HOME"
+    rlAssertGrep "JAVA_HOME is /usr/lib/jvm/jre-21-openjdk" $rlRun_LOG
+    unset JAVA_HOME
+    export _prefer_jre=false
+    rlRun -s ". /usr/share/java-utils/java-functions && set_jvm && echo JAVA_HOME is \$JAVA_HOME"
+    rlAssertGrep "JAVA_HOME is /usr/lib/jvm/java-21-openjdk" $rlRun_LOG
+  rlPhaseEnd
+
+rlJournalEnd
+rlJournalPrintText