\documentclass{testsuite}
\usepackage{fontspec}
\begin{document}
\def\text{\fbox{\parbox{1.55cm}{%
  EXAMPLE HYPHENATION%
}}\hfill}

\fontspec{TeX Gyre Termes}
\addfontfeature{HyphenChar=None}
\text
\addfontfeature{HyphenChar={+}}
\text
\addfontfeature{HyphenChar={"2A}}
\text
\end{document}