彩盒内缺线

Question

我正在为定理创建框。我的代码如下：

\usepackage[many]{tcolorbox}

\newtcolorbox[auto counter]{pro}[2][]{colframe=blue,colback=white,rightrule=0pt,
  toprule=3pt,title={Proposition \thetcbcounter\ #2},coltitle={black},sharp corners,
  frame style={left color=black,right color=black},
  #1}

\begin{document}

\begin{pro}{}
test
\end{pro}

\end{document}

我怎样才能将缺失的行放在右边？