Verify that date/number translations exist for all supported languages (#23692)

packages/flutter_localizations/test/translations_test.dart

@@ -74,6 +74,17 @@ void main() {
       expect(localizations.tabLabel(tabIndex: 2, tabCount: 5), isNot(contains(r'$tabCount')));
       expect(() => localizations.tabLabel(tabIndex: 0, tabCount: 5), throwsAssertionError);
       expect(() => localizations.tabLabel(tabIndex: 2, tabCount: 0), throwsAssertionError);
+
+      expect(localizations.formatHour(const TimeOfDay(hour: 10, minute: 0)), isNotNull);
+      expect(localizations.formatMinute(const TimeOfDay(hour: 10, minute: 0)), isNotNull);
+      expect(localizations.formatYear(DateTime(2018, 8, 1)), isNotNull);
+      expect(localizations.formatMediumDate(DateTime(2018, 8, 1)), isNotNull);
+      expect(localizations.formatFullDate(DateTime(2018, 8, 1)), isNotNull);
+      expect(localizations.formatMonthYear(DateTime(2018, 8, 1)), isNotNull);
+      expect(localizations.narrowWeekdays, isNotNull);
+      expect(localizations.narrowWeekdays.length, 7);
+      expect(localizations.formatDecimal(123), isNotNull);
+      expect(localizations.formatTimeOfDay(const TimeOfDay(hour: 10, minute: 0)), isNotNull);
     });
   }