public function testAssemble()
{
$selector = new SubStringSelectExpression();
$selector->setField('fieldname');
$this->assertEquals('SUBSTRING(fieldname,0)', QueryAssembler::stringify($selector));
$selector->setAlias('new');
$this->assertEquals('SUBSTRING(fieldname,0) AS new', QueryAssembler::stringify($selector));
$selector->setStartPosition(10);
$this->assertEquals('SUBSTRING(fieldname,10) AS new', QueryAssembler::stringify($selector));
$selector->setLength(5);
$this->assertEquals('SUBSTRING(fieldname,10,5) AS new', QueryAssembler::stringify($selector));
}
