/**
* Test purge method
*/
public function testPurge()
{
$this->appResourceMock->expects($this->once())->method('getConnection')->will($this->returnValue($this->adapterMock));
$this->appResourceMock->expects($this->once())->method('getTableName')->will($this->returnValue('sales_invoice_grid'));
$this->adapterMock->expects($this->once())->method('delete')->with('sales_invoice_grid', ['fi.field = ?' => 1])->will($this->returnValue(1));
$this->assertEquals(1, $this->grid->purge(1, 'fi.field'));
}