PHPUnit Zend_Test_PHPUnit_DatabaseTestCase fails to truncate table

I am setting up some db integration testing using Zend_Test_PHPUnit_DatabaseTestCase.

My tests run but the db tables do not get truncated so an add test fails assertion - as the xml I provide as a dataset does not match the db can anybody suggest why

TestCase

  class ArtworkDBTest extends DatabaseTestCase
    { 
public function testAddArtwork()
            {

                $data=array("artwork_name"=>'test',"description"=>'test',"imgpath"=>'test',"size"=>'test',"price_information"=>'test',"category"=>1,"artwork_order"=>1);

                $mockedLog=$this->getMock("Log",array("log"));

                $artwork = new shop_Artwork($mockedLog,Zend_Db_Table_Abstract::getDefaultAdapter()); 

                $artwork->addArtwork($data); 


                $this->assertDataSetsMatchXML('artwork-add.xml',  $dataSet);


            }
}

Database testing setup code (adapted from dragonbe and ibuildings tutorials)

abstract class DatabaseTestCase extends Zend_Test_PHPUnit_DatabaseTestCase
{
 const DEFAULT_CONNECTION_SCHEMA = 'main';

            protected $_connectionMock;
            private $__configuration = N开发者_C百科ULL;
            protected $_connectionSchema = self::DEFAULT_CONNECTION_SCHEMA;
            protected $_seedFilesPath;
            protected $dataSet;

   public function __construct()
   {
          $this->dataSet = new Zend_Test_PHPUnit_Db_DataSet_QueryDataSet($this->getConnection());

          $this->dataSet->addTable('artwork','Select* from artwork');
          $this->dataSet->addTable('login','Select *from login');
          $this->dataSet->addTable('category','Select *from category'); 
   }  

    public function getConfiguration()
    {

        if ($this->__configuration == NULL) {
            $this->__configuration = new Zend_Config_Ini(TEST_PATH . '/application/configs/tests.ini');
        }

        return $this->__configuration;
    }

    public function getSeedFilesPath()
    {
        if ($this->_seedFilesPath == NULL) {
            $this->_seedFilesPath = $this->getConfiguration()->tests->seeds->folder;
        }

        return rtrim($this->_seedFilesPath, '/') . '/';
    }


    protected function getConnection()
    {

        if ($this->_connectionMock == NULL) {
            $dbAdapterName = $this->getConfiguration()->tests->dbadapter;
            $dbAdapterParams = $this->getConfiguration()->tests->dbparams->toArray();

            $connection = Zend_Db::factory($dbAdapterName, $dbAdapterParams);


            $this->_connectionMock = $this->createZendDbConnection(
                $connection, $this->_connectionSchema
            );




            Zend_Db_Table_Abstract::setDefaultAdapter($connection);


        }
        return $this->_connectionMock;
    }


    protected function getDataSet()
    {
        return $this->createFlatXMLDataSet(TEST_PATH . '/fixtures/models/artwork-seed.xml');
    }



 /**
     * Convert a Rowset to a Dataset
     *
     * @param  Zend_Db_Table_Rowset_Abstract $rowset
     * @param  string $tableName
     * @return PHPUnit_Extensions_Database_DataSet_DefaultDataSet
     */
    public function convertRowsetToDataSet($rowset, $tableName = NULL)
    {
        $rowsetDataSet = new Zend_Test_PHPUnit_Db_DataSet_DbRowset($rowset, $tableName);
        return new PHPUnit_Extensions_Database_DataSet_DefaultDataSet(array($rowsetDataSet));
    }

    /**
     * Convert a Record to a Dataset
     *
     * @param  array $data
     * @param  string $tableName
     * @return PHPUnit_Extensions_Database_DataSet_DefaultDataSet
     */
    public function convertRecordToDataSet(Array $data, $tableName)
    {
        $rowset = new Zend_Db_Table_Rowset(array('data' => array($data)));
        return $this->convertRowsetToDataSet($rowset, $tableName);
    }

    /**
     * Compare dataset with data stored in the file
     *
     * @param  string $filename
     * @param  PHPUnit_Extensions_Database_DataSet_IDataSet $expected
     * @return boolean
     */
    public function assertDataSetsMatchXML($filename, PHPUnit_Extensions_Database_DataSet_IDataSet $actual)
    {
        if (empty($filename) || !is_string($filename))
                throw new InvalidArgumentException(
                  'Second parameter "filename" is not a valid string.'
                );

        $expected = $this->createFlatXmlDataSet($this->getSeedFilesPath() . $filename);

        return $this->assertDataSetsEqual($expected, $actual);
    }
}

The answer was running parent::setUp(); inside the test class's setUp() method