Lists, counters, and refs

Question

I'm trying to create an environment containing a single-instance, numbered list (so that I can easily control the spacing, etc.). The problem is that I cannot used \ref to cross-ref to the enumerated item.

The code of a MWE is:

\documentclass{article}    
\newcounter{tesisc}
\AtBeginDocument{\setcounter{tesisc}{1}}
\newenvironment*{Tesis}
  {\begin{list}
    {$(\arabic{tesisc})$}
    {\setlength{\rightmargin}{0cm}
     \setlength{\leftmargin}{2\parindent}}
    \item
  }
  {\end{list}\refstepcounter{tesisc}}
\begin{document}
\begin{Tesis}
  Testing testing testing testing testing testing testing testing testing testing.
  \label{th:one}
\end{Tesis}
\begin{Tesis}
  Testing testing testing testing testing testing testing testing testing testing.
  \label{th:two}
\end{Tesis}
This is one reference: \ref{th:one}. This is another reference: \ref{th:two}.
\end{document}

My environment numbering works fine, but not the cross-referencing.

How can I tweak my definition in order for my references work?

Answer 1

You need to move the \refstepcounter earlier, or as here use \usecounter so list sets up \item to increment the counter.

\documentclass{article}    
\newcounter{tesisc}

\newenvironment*{Tesis}
  {\begin{list}
    {$(\arabic{tesisc})$}
    {\setlength{\rightmargin}{0cm}
     \refstepcounter{tesisc}\setlength{\leftmargin}{2\parindent}}
    \item
  }
  {\end{list}}
\begin{document}
\begin{Tesis}
  Testing testing testing testing testing testing testing testing testing testing.
  \label{th:one}
\end{Tesis}
\begin{Tesis}
  Testing testing testing testing testing testing testing testing testing testing.
  \label{th:two}
\end{Tesis}
This is one reference: \ref{th:one}. This is another reference: \ref{th:two}.
\end{document}