BibTex Error - .bbl' not created by bib latex

The .bbl files created by a normal BibTeX run and a Biber run (or BibTeX with biblatex) are completely different and they are not compatible with each other.

Surely you've used a file where a "normal" bibliography was used and afterwards you've switched to biblatex.

That's why biblatex is complaining that the .bbl file has not been created by it.

The solution is to delete the .bbl file and run pdflatex and Biber again.

This is the contents of the .bbl file generated by biblatex with Biber from your bibliography:

% $ biblatex auxiliary file $
% $ biblatex bbl format version 2.3 $
% Do not modify the above lines!
%
% This is an auxiliary file used by the 'biblatex' package.
% This file may safely be deleted. It will be recreated by
% biber as required.
%
\begingroup
\makeatletter
\@ifundefined{[email protected]}
  {\@latex@error
     {Missing 'biblatex' package}
     {The bibliography requires the 'biblatex' package.}
      \aftergroup\endinput}
  {}
\endgroup


\refsection{0}
  \sortlist{entry}{nyt}
    \entry{zappone2009supermarketduopoly}{online}{}
      \name{labelname}{1}{}{%
        {{uniquename=0,hash=af62e8eb39454b026c19a85900defef2}{Zappone}{Z\bibinitperiod}{C.}{C\bibinitperiod}{}{}{}{}}%
      }
      \name{author}{1}{}{%
        {{uniquename=0,hash=af62e8eb39454b026c19a85900defef2}{Zappone}{Z\bibinitperiod}{C.}{C\bibinitperiod}{}{}{}{}}%
      }
      \strng{namehash}{af62e8eb39454b026c19a85900defef2}
      \strng{fullhash}{af62e8eb39454b026c19a85900defef2}
      \field{sortinit}{Z}
      \field{labelyear}{2009}
      \field{datelabelsource}{}
      \field{labeltitle}{Supermarket duopoly blamed for soaring food prices}
      \field{title}{Supermarket duopoly blamed for soaring food prices}
      \field{urlday}{03}
      \field{urlmonth}{29}
      \field{urlyear}{2014}
      \field{year}{2009}
      \verb{url}
      \verb http://www.smh.com.au/business/supermarket-duopoly-blamed-for-soaring-food-%20prices-20091109-i3tn.html
      \endverb
    \endentry
  \endsortlist
\endrefsection
\endinput

As you can see, it doesn't even contain the thebibliography environment...

As a side note, when using biblatex, it is recommended to use

\addbibresource{bibtest.bib}

instead of

\bibliography{bibtest}

The latter works for compatibility only.

You have to write \addbibresource{bibtest.bib} (with the .bib extension) instead of \bibliography{bibtest}(without the extension).