public function test_isoDateTime_basics()
 {
     $this->assertEquals(DateTimeFormatter::ISO_DATE_TIME()->getChronology(), IsoChronology::INSTANCE());
     $this->assertEquals(DateTimeFormatter::ISO_DATE_TIME()->getZone(), null);
     $this->assertEquals(DateTimeFormatter::ISO_DATE_TIME()->getResolverStyle(), ResolverStyle::STRICT());
 }