function testGetFieldDataForCSVPreview()
 {
     $f = new Tracker_FormElement_Field_DateTestVersion();
     $f->setReturnValueAt(0, '_getUserCSVDateFormat', 'day_month_year');
     $f->setReturnValueAt(1, '_getUserCSVDateFormat', 'month_day_year');
     $f->setReturnValueAt(2, '_getUserCSVDateFormat', 'day_month_year');
     $f->setReturnValueAt(3, '_getUserCSVDateFormat', 'day_month_year');
     $this->assertEqual('1981-04-25', $f->getFieldDataForCSVPreview('25/04/1981'));
     $this->assertEqual('1981-04-25', $f->getFieldDataForCSVPreview('04/25/1981'));
     $this->assertNull($f->getFieldDataForCSVPreview('35/44/1981'));
     // this function check date validity!
     $this->assertNull($f->getFieldDataForCSVPreview(''));
 }