[LANG-1791] Add test

See https://issues.apache.org/jira/browse/LANG-1791

Author: garydgregory

src/test/java/org/apache/commons/lang3/time/FastDateFormatTest.java

@@ -31,7 +31,6 @@
 import java.time.Instant;
 import java.time.LocalDate;
 import java.time.ZoneId;
-import java.time.ZoneOffset;
 import java.time.format.DateTimeFormatter;
 import java.util.Calendar;
 import java.util.Date;
@@ -282,6 +281,23 @@ void testLang1641() {
                 FastDateFormat.getInstance(ISO_8601_DATE_FORMAT, TimeZone.getTimeZone("Australia/Yancowinna")));
     }
 
+    /**
+     * See LANG-1791 https://issues.apache.org/jira/browse/LANG-1791.
+     */
+    @Test
+    @DefaultTimeZone("America/Toronto")
+    void testLang1791() {
+        final Instant now = Instant.now();
+        final String pattern = "yyyyMMddHH";
+        final FastDateFormat gmtFormatter = FastDateFormat.getInstance(pattern, TimeZones.GMT);
+        final Calendar gmtCal = Calendar.getInstance(TimeZones.GMT);
+        final String gmtString = gmtFormatter.format(gmtCal);
+        assertEquals(DateTimeFormatter.ofPattern(pattern).withZone(ZoneId.of("GMT")).format(now), gmtString);
+        final FastDateFormat defaultFormatter = FastDateFormat.getInstance(pattern);
+        final String defaultString = defaultFormatter.format(gmtCal);
+        assertEquals(DateTimeFormatter.ofPattern(pattern).withZone(ZoneId.systemDefault()).format(now), defaultString);
+    }
+
     /**
      * According to LANG-954 (https://issues.apache.org/jira/browse/LANG-954) this is broken in Android 2.1.
      */
@@ -388,27 +404,4 @@ void testTimeDefaults() {
         assertEquals(FastDateFormat.getTimeInstance(FastDateFormat.LONG),
                 FastDateFormat.getTimeInstance(FastDateFormat.LONG, TimeZone.getDefault(), Locale.getDefault()));
     }
-
-    /*
-    * org.apache.commons.lang3.time.FastDateFormat
-    * In dateFormatter.format(timeCal), when time was not set explicitly, would make e.g.
-    * the following timestamps in Toronto at 10 am on 2025-09-17:
-    * "2025091714" - GMT, as expected, when using commons-lang3 v3.0.1
-    * "2025091710" - EDT, when using commons-lang3 v3.18.0 or 3.19.0 (likely some other versions <3.18.0 too, but I did not test that)
-    */
-    @Test
-    public void fastDateFormatFormatterUsingCalendarShouldMakeGmtTimestamp() {
-        final Instant now = Instant.now();
-        final ZoneId zoneId = ZoneId.systemDefault(); // e.g. America/Toronto
-        final ZoneOffset offset = zoneId.getRules().getOffset(now);
-        System.out.printf("Current time: %s, zone: %s, offset: %sh\n", now, zoneId, offset);
-        // some legacy code that should still work the same after commons-lang3 minor ver. upgrade but it does not:
-        final FastDateFormat dateFormatter = FastDateFormat.getInstance("yyyyMMddHH");
-        final TimeZone timeZone = TimeZone.getTimeZone("GMT");
-        final Calendar timeCal = Calendar.getInstance(timeZone);
-        final String timestamp = dateFormatter.format(timeCal); // makes local zone timestamp when commons-lang3 v3.18.0, 3.19.0 is used (ignores Calendar's zone).
-        // expected GMT timestamp
-        final String expected = DateTimeFormatter.ofPattern("yyyyMMddHH").withZone(ZoneId.of("GMT")).format(now);
-        assertEquals(expected, timestamp);
-    }
 }