\def\foo{foo-test}
\def\bar{bar-test}

\part{test heading foo-test}
\label{testheadingfoo}

\part{test heading}
\label{foo}

\part{Tables}
\label{tables}

\begin{table}[htbp]
\begin{minipage}{\linewidth}
\setlength{\tymax}{0.5\linewidth}
\centering
\small
\caption{Prototype table caption foo-test}
\label{prototypetablecaptionfoo}
\begin{tabulary}{\textwidth}{@{}LCR@{}} \toprule
&\multicolumn{2}{c}{Grouping}\\
First Header&Second Header&Third Header\\
\midrule
Content&\multicolumn{2}{c}{\emph{Long Cell}}\\
Content&\textbf{Cell}&Cell\\

\midrule
New section&More&Data\\
And more&\multicolumn{2}{c}{With an escaped `\textbar{}'}\\

\bottomrule

\end{tabulary}
\end{minipage}
\end{table}
\end{document}