System.Assert Assertion in Delphi

var
  List: TStringList;

procedure TForm1.FormCreate (Sender: TObject);
begin
 // Assert (Assigned (List)); // The second parameter defaults to 'Assertion failure'
  Assert (Assigned (List), 'List object was not created');
end ;

You can use {$ ASSERTIONS OFF / ON} to decide whether to enable Assert; by default, it is only used for the Debug version.