commit 4a34ffb129268d082a4a8be34f0c8c967d7a74c4
Author: BERNARD Adrien <abernard@murex.com>
Date:   Fri Jan 2 17:51:51 2026 +0100

    Test custom exception logging

diff --git a/log4j-core-test/src/test/java/org/apache/logging/log4j/core/pattern/CustomizedThrowableTest.java b/log4j-core-test/src/test/java/org/apache/logging/log4j/core/pattern/CustomizedThrowableTest.java
new file mode 100644
index 0000000000..87342031f5
--- /dev/null
+++ b/log4j-core-test/src/test/java/org/apache/logging/log4j/core/pattern/CustomizedThrowableTest.java
@@ -0,0 +1,70 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to you under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.logging.log4j.core.pattern;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.List;
+import org.apache.logging.log4j.Logger;
+import org.apache.logging.log4j.core.LoggerContext;
+import org.apache.logging.log4j.core.test.appender.ListAppender;
+import org.apache.logging.log4j.core.test.junit.LoggerContextSource;
+import org.apache.logging.log4j.core.test.junit.Named;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+/**
+ * Unit tests for {@code throwable} pattern.
+ */
+@LoggerContextSource("log4j-throwable-default.xml")
+public class CustomizedThrowableTest {
+    private ListAppender app;
+    private Logger logger;
+
+    @BeforeEach
+    public void setUp(final LoggerContext context, @Named("List") final ListAppender app) {
+        this.logger = context.getLogger("LoggerTest");
+        this.app = app.clear();
+    }
+
+    @Test
+    public void testException() {
+        final Throwable exception = new CustomException("This is an error message", "ERROR_CODE");
+        logger.error("Exception", exception);
+        final List<String> msgs = app.getMessages();
+        assertNotNull(msgs);
+        assertEquals(1, msgs.size(), "Incorrect number of messages. Should be 1 is " + msgs.size());
+        assertTrue(msgs.get(0).contains("Code: ERROR_CODE; This is an error message"), msgs.get(0));
+    }
+
+    private static class CustomException extends Exception {
+
+        private String errorCode;
+
+        public CustomException(String message, String errorCode) {
+            super(message);
+            this.errorCode = errorCode;
+        }
+
+        @Override
+        public String toString() {
+            return getClass().getName() + ": Code: " + errorCode + "; " + getMessage();
+        }
+    }
+}
diff --git a/log4j-core-test/src/test/resources/log4j-throwable-default.xml b/log4j-core-test/src/test/resources/log4j-throwable-default.xml
new file mode 100644
index 0000000000..bf61e248ea
--- /dev/null
+++ b/log4j-core-test/src/test/resources/log4j-throwable-default.xml
@@ -0,0 +1,39 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  ~ Licensed to the Apache Software Foundation (ASF) under one or more
+  ~ contributor license agreements.  See the NOTICE file distributed with
+  ~ this work for additional information regarding copyright ownership.
+  ~ The ASF licenses this file to you under the Apache License, Version 2.0
+  ~ (the "License"); you may not use this file except in compliance with
+  ~ the License.  You may obtain a copy of the License at
+  ~
+  ~      http://www.apache.org/licenses/LICENSE-2.0
+  ~
+  ~ Unless required by applicable law or agreed to in writing, software
+  ~ distributed under the License is distributed on an "AS IS" BASIS,
+  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  ~ See the License for the specific language governing permissions and
+  ~ limitations under the License.
+  -->
+<Configuration status="OFF" name="XMLConfigTest">
+  <Properties>
+    <Property name="filters">org.junit,org.apache.maven,sun.reflect,java.lang.reflect</Property>
+  </Properties>
+  <ThresholdFilter level="debug"/>
+
+  <Appenders>
+    <Console name="STDOUT">
+      <PatternLayout pattern="%m%n%throwable"/>
+    </Console>
+    <List name="List">
+      <PatternLayout pattern="%m%n%throwable"/>
+    </List>
+  </Appenders>
+
+  <Loggers>
+    <Root level="error">
+      <AppenderRef ref="List"/>
+    </Root>
+  </Loggers>
+
+</Configuration>