documentclass{scrartcl}
usepackage[english]{babel}
usepackage[backend=bibtex]{biblatex}

bibliography{test}

begin{document}
title{A test paper}
date{}
maketitle

This is a sentence quoting cite{testpaper}.

printbibliography
end{document}

@article{testpaper,
    author = {George Testpaper},
    year = {2015},
    pages = {229--252},
    journal = {Testjournal},
    volume = {56},
    number = {3},
    title = {Some other testpaper}
}

documentclass{scrartcl}
usepackage[english]{babel}
usepackage[backend=bibtex]{biblatex}

begingroup
makeatletter
@ifundefined{ver@biblatex.sty}
  {@latex@error
     {Missing 'biblatex' package}
     {The bibliography requires the 'biblatex' package.}
      aftergroupendinput}
  {}
endgroup%I tried removing everything between "begingroup" and "endgroup" without success

entry{testpaper}{article}{}
  name{author}{1}{}{%
    {{}%
     {Testpaper}{T.}%
     {George}{G.}%
     {}{}%
     {}{}}%
  }
  strng{namehash}{TG1}
  strng{fullhash}{TG1}
  field{sortinit}{T}
  field{number}{3}
  field{pages}{229bibrangedash 252}
  field{title}{Some other testpaper}
  field{volume}{56}
  field{journaltitle}{Testjournal}
  field{year}{2015}
endentry

lossort
endlossort

endinput%I tried removing this line without success

begin{document}
title{A test paper}
date{}
maketitle

This is a sentence quoting cite{testpaper}.

printbibliography
end{document}

! Undefined control sequence.
l.15 entry
{testpaper}{article}{}
The control sequence at the end of the top line
of your error message was never def'ed.