Index: trunk/test/unit/org/openstreetmap/josm/tools/JosmDecimalFormatSymbolsProviderTest.java
===================================================================
--- trunk/test/unit/org/openstreetmap/josm/tools/JosmDecimalFormatSymbolsProviderTest.java	(revision 16658)
+++ trunk/test/unit/org/openstreetmap/josm/tools/JosmDecimalFormatSymbolsProviderTest.java	(revision 16660)
@@ -3,6 +3,9 @@
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertTrue;
 
+import java.text.DecimalFormat;
 import java.util.Locale;
+import java.util.stream.Stream;
 
 import org.junit.Rule;
@@ -24,4 +27,17 @@
     public JOSMTestRules test = new JOSMTestRules();
 
+    @Test
+    public void testGroupingSeparator() {
+        checkGroupingSymbol(Locale.ROOT);
+        assertTrue(I18n.getAvailableTranslations().count() > 10);
+        I18n.getAvailableTranslations().forEach(this::checkGroupingSymbol);
+        Stream.of("", "AU", "IE", "US", "UK").map(country -> new Locale("en", country, "")).forEach(this::checkGroupingSymbol);
+        Stream.of("", "AT", "CH", "DE").map(country -> new Locale("de", country, "")).forEach(this::checkGroupingSymbol);
+    }
+
+    private void checkGroupingSymbol(Locale locale) {
+        assertEquals(locale.toString(), "123\u202F456", DecimalFormat.getInstance(locale).format(123_456));
+    }
+
     /**
      * Test {@link JosmDecimalFormatSymbolsProvider#parseDouble}.