When I redefine the style of the chapter, the name of the table of contents (at the top of the table) is not displayed.

If I have understand well, the style of the table of contents is defined by the style of the chapter. But it doesn't matter the style I use, it's never displayed.

Do you have any idea, what can cause that ? Is a package missing ?

\documentclass[11pt]{report}
\usepackage[francais]{babel}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[usenames,dvipsnames]{xcolor}
\usepackage[explicit]{titlesec}
\usepackage{titletoc}

\titleformat{\chapter}[block]
{\begin{picture}(330,180)} {%
\put(0,230){%
\makebox(0,0)[lb]{%
\colorbox[named]{Aquamarine}{\Huge \textcolor{white}{\thechapter}}
}
}
\textcolor[named]{Aquamarine}{\sc{\put(40,235){\parbox[t]{300pt}{\huge\filright #1}}}}
}
{0pt}{}
[\end{picture}]
\titlespacing*{\chapter}{0pt}{50pt}{-200pt}

\begin{document}
\tableofcontents
\chapter{TestChapter}
\section{TestSection}
\chapter{Test}
\end{document}


You should use the numberless key since the table of contents is a numberless chapter, like this:
\titleformat{name=\chapter, numberless}[block]{...}{}{0pt}{...}