function testConstructorHandlesEmptyStartAndEndTimesCorrectly()
 {
     $expected_record = array('uid' => $this->expected_uid, 'jobid' => $this->expected_jobid);
     $mapping = new TZUserJobMapping($expected_record);
     $this->assertNull($mapping->getStartTime());
     $this->assertNull($mapping->getEndTime());
 }