LOG4J2-3885: Add test for ISO8601_OFFSET_DATE_TIME_HH with system default zone

Ensure legacy and modern formatting produce consistent results
when the system default zone offset is a whole hour.
Skip the test otherwise using assumptions.

Author: ramanathan1504

log4j-core-test/src/test/java/org/apache/logging/log4j/core/pattern/NamedInstantPatternTest.java

@@ -17,11 +17,13 @@
 package org.apache.logging.log4j.core.pattern;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assumptions.assumeThat;
 
 import java.time.Instant;
+import java.time.ZoneId;
+import java.time.ZoneOffset;
 import org.apache.logging.log4j.core.time.MutableInstant;
 import org.apache.logging.log4j.core.util.internal.instant.InstantPatternFormatter;
-import org.junit.jupiter.api.Assumptions;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.EnumSource;
 
@@ -30,6 +32,15 @@ class NamedInstantPatternTest {
     @ParameterizedTest
     @EnumSource(NamedInstantPattern.class)
     void compatibilityOfLegacyPattern(NamedInstantPattern namedPattern) {
+        if (namedPattern == NamedInstantPattern.ISO8601_OFFSET_DATE_TIME_HH) {
+            ZoneOffset offset = ZoneId.systemDefault().getRules().getOffset(Instant.now());
+            assumeThat(offset.getTotalSeconds() % 3600 == 0)
+                    .withFailMessage(
+                            "Skipping test: ISO8601_OFFSET_DATE_TIME_HH requires a whole-hour offset, but system offset is %s",
+                            offset)
+                    .isTrue();
+        }
+
         InstantPatternFormatter legacyFormatter = InstantPatternFormatter.newBuilder()
                 .setPattern(namedPattern.getLegacyPattern())
                 .setLegacyFormattersEnabled(true)
@@ -43,17 +54,6 @@ void compatibilityOfLegacyPattern(NamedInstantPattern namedPattern) {
         instant.initFromEpochSecond(javaTimeInstant.getEpochSecond(), javaTimeInstant.getNano());
         String legacy = legacyFormatter.format(instant);
         String modern = formatter.format(instant);
-        if (namedPattern == NamedInstantPattern.ISO8601_OFFSET_DATE_TIME_HH) {
-            java.time.ZoneOffset offset =
-                    java.time.ZoneId.systemDefault().getRules().getOffset(java.time.Instant.now());
-            Assumptions.assumeTrue(
-                    offset.getTotalSeconds() % 3600 == 0,
-                    () -> String.format(
-                            "Skipping test: ISO8601_OFFSET_DATE_TIME_HH requires a whole-hour offset, but system offset is %s",
-                            offset));
-            assertThat(legacy).isEqualTo(modern);
-        } else {
-            assertThat(legacy).isEqualTo(modern);
-        }
+        assertThat(legacy).isEqualTo(modern);
     }
 }