From 78023a9d10f674437063ef112a2452127dd6d52d Mon Sep 17 00:00:00 2001
From: Tanmay Baid <tanmay@amazon.com>
Date: Wed, 17 Sep 2025 22:13:52 -0700
Subject: [PATCH] Add new date pattern for DatePatternConverterTestBase and add
 new test class for LegacyInstantFormatter reprodcing bug #3667

---
 .../pattern/DatePatternConverterTestBase.java | 13 ++++++++
 ...nverterWithLegacyInstantFormatterTest.java | 32 +++++++++++++++++++
 2 files changed, 45 insertions(+)
 create mode 100644 log4j-core-test/src/test/java/org/apache/logging/log4j/core/pattern/DatePatternConverterWithLegacyInstantFormatterTest.java

diff --git a/log4j-core-test/src/test/java/org/apache/logging/log4j/core/pattern/DatePatternConverterTestBase.java b/log4j-core-test/src/test/java/org/apache/logging/log4j/core/pattern/DatePatternConverterTestBase.java
index 16fd89ac30b..64fbbb3da88 100644
--- a/log4j-core-test/src/test/java/org/apache/logging/log4j/core/pattern/DatePatternConverterTestBase.java
+++ b/log4j-core-test/src/test/java/org/apache/logging/log4j/core/pattern/DatePatternConverterTestBase.java
@@ -32,6 +32,7 @@
 import org.apache.logging.log4j.core.time.Instant;
 import org.apache.logging.log4j.core.time.MutableInstant;
 import org.apache.logging.log4j.core.util.Constants;
+import org.apache.logging.log4j.core.util.internal.instant.InstantPatternFormatter;
 import org.apache.logging.log4j.util.Strings;
 import org.junit.jupiter.api.Test;
 
@@ -67,9 +68,15 @@ public long getTimeMillis() {
     private static final String[] ISO8601_FORMAT_OPTIONS = {ISO8601};
 
     private final boolean threadLocalsEnabled;
+    private final boolean legacyFormatterEnabled;
 
     DatePatternConverterTestBase(final boolean threadLocalsEnabled) {
+        this(threadLocalsEnabled, false);
+    }
+
+    DatePatternConverterTestBase(final boolean threadLocalsEnabled, final boolean legacyFormatterEnabled) {
         this.threadLocalsEnabled = threadLocalsEnabled;
+        this.legacyFormatterEnabled = legacyFormatterEnabled;
     }
 
     private static Date date(final int year, final int month, final int date) {
@@ -84,6 +91,11 @@ void testThreadLocalsConstant() {
         assertEquals(Constants.ENABLE_THREADLOCALS, threadLocalsEnabled);
     }
 
+    @Test
+    void testInstantFormatterConstant() {
+        assertEquals(InstantPatternFormatter.LEGACY_FORMATTERS_ENABLED, legacyFormatterEnabled);
+    }
+
     @Test
     void testFormatDateStringBuilderDefaultPattern() {
         assertDatePattern(null, date(2001, 1, 1), "2001-02-01 14:15:16,123");
@@ -163,6 +175,7 @@ void testFormatAmericanPatterns() {
         assertDatePattern("dd/MM/yyyy HH:mm:ss.SSSSSS", date, "11/03/2011 14:15:16.123000");
         assertDatePattern("dd/MM/yy HH:mm:ss.SSS", date, "11/03/11 14:15:16.123");
         assertDatePattern("dd/MM/yy HH:mm:ss.SSSSSS", date, "11/03/11 14:15:16.123000");
+        assertDatePattern("EEE, dd MMM yyyy HH:mm:ss zzz", date, "Fri, 11 Mar 2011 14:15:16 PST");
     }
 
     @SuppressWarnings("deprecation")
diff --git a/log4j-core-test/src/test/java/org/apache/logging/log4j/core/pattern/DatePatternConverterWithLegacyInstantFormatterTest.java b/log4j-core-test/src/test/java/org/apache/logging/log4j/core/pattern/DatePatternConverterWithLegacyInstantFormatterTest.java
new file mode 100644
index 00000000000..b558c4f616f
--- /dev/null
+++ b/log4j-core-test/src/test/java/org/apache/logging/log4j/core/pattern/DatePatternConverterWithLegacyInstantFormatterTest.java
@@ -0,0 +1,32 @@
+/*
+ * 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 org.apache.logging.log4j.test.junit.SetTestProperty;
+import org.apache.logging.log4j.test.junit.UsingTestProperties;
+
+@SetTestProperty.SetTestProperties(value = {
+        @SetTestProperty(key = "log4j2.enable.threadlocals", value = "false"),
+        @SetTestProperty(key = "log4j2.instantFormatter", value = "legacy")
+})
+@UsingTestProperties
+class DatePatternConverterWithLegacyInstantFormatterTest extends DatePatternConverterTestBase {
+
+    DatePatternConverterWithLegacyInstantFormatterTest() {
+        super(false, true);
+    }
+}