public function testMapFieldWithId($cm)
{
$cm->mapField(array('fieldName' => 'id', 'id' => true));
$this->assertTrue(isset($cm->fieldMappings['id']));
$this->assertEquals(array('jsonName' => '_id', 'id' => true, 'type' => 'string', 'fieldName' => 'id'), $cm->fieldMappings['id']);
$this->assertEquals('id', $cm->identifier);
$this->assertEquals(array('_id' => 'id'), $cm->jsonNames);
return $cm;
}