added simple test for appender definitiob via file inclusion

Signed-off-by: ceki <ceki@qos.ch>

Author: ceki

logback-classic-blackbox/src/test/blackboxInput/joran/incl/includedListAppender.xml

@@ -0,0 +1,5 @@
+<included>
+
+    <appender name="LIST" class="ch.qos.logback.core.read.ListAppender"/>
+
+</included>

logback-classic-blackbox/src/test/blackboxInput/joran/incl/topAppender.xml

@@ -0,0 +1,25 @@
+<!--
+  ~ Logback: the reliable, generic, fast and flexible logging framework.
+  ~ Copyright (C) 1999-2026, QOS.ch. All rights reserved.
+  ~
+  ~ This program and the accompanying materials are dual-licensed under
+  ~ either the terms of the Eclipse Public License v2.0 as published by
+  ~ the Eclipse Foundation
+  ~
+  ~   or (per the licensee's choosing)
+  ~
+  ~ under the terms of the GNU Lesser General Public License version 2.1
+  ~ as published by the Free Software Foundation.
+  -->
+
+<configuration>
+
+    <variable scope="system" name="JO_PREFIX" value="src/test/blackboxInput/joran"/>
+
+    <include file="${JO_PREFIX}/incl/includedListAppender.xml" />
+
+    <root level="TRACE">
+        <appender-ref ref="LIST" />
+    </root>
+
+</configuration>

logback-classic-blackbox/src/test/java/ch/qos/logback/classic/blackbox/joran/BlackboxJoranConfiguratorTest.java

@@ -207,6 +207,21 @@ void verifyJULLevel(String loggerName, Level expectedLevel) {
         }
     }
 
+    @Test
+    public void includedAppender() throws JoranException {
+        String configFileAsStr = BlackboxClassicTestConstants.JORAN_INPUT_PREFIX + "incl/topAppender.xml";
+        configure(configFileAsStr);
+
+        ListAppender<?> listAppender = (ListAppender<?>) root.getAppender("LIST");
+        assertNotNull(listAppender);
+
+        logger.debug("includedAppender");
+
+        assertEquals(1, listAppender.list.size());
+        assertEquals(Level.TRACE, root.getLevel());
+
+    }
+
     // See https://github.com/qos-ch/logback/issues/1001
     // See https://github.com/qos-ch/logback/issues/997
     @Test

logback-core/src/main/java/ch/qos/logback/core/model/processor/IncludeModelHandler.java

@@ -106,6 +106,8 @@ public Model buildModelFromIncludedFile(ContextAwarePropertyContainer capc, URL
             return null;
         }
 
+        addInfo("Including configuration file [" + inputURL + "]");
+
         SaxEventRecorder recorder = null;
 
         try {