Doctrine\OXM\Types\DateTimeTzType::convertToXmlValue PHP Method

    public function convertToXmlValue($value)
    {
        return $value !== null ? $value->format(static::FORMAT) : null;
    }

 public function testDateTimeConvertsToXmlValue()
 {
     $date = new \DateTime('1985-09-01 10:10:10+0200');
     $expected = '1985-09-01 10:10:10+0200';
     $actual = $this->_type->convertToXmlValue($date);
     $this->assertEquals($expected, $actual);
 }