Tikz geschweifte Klammer unter Zeichnung

\draw[thick,red,decorate,decoration={brace,amplitude=12pt}] (current axis.south east) -- (current axis.south west) node[midway, below,yshift=-12pt]{Test};

\documentclass{article}

\usepackage{pgfplots}% lädt auch tikz
\pgfplotsset{compat=newest}
\usetikzlibrary{decorations.pathreplacing,calc}

\begin{document}
\begin{tikzpicture}

\begin{axis}[%
width=8cm,
height=6cm,
scale only axis,
xmin=0,
xmax=936,
ymin=0.1,
ymax=1,
x tick label style={/pgf/number format/1000 sep=}
]
\addplot [
color=blue,
solid,
line width=1.1pt,
forget plot
]
table[row sep=crcr]{
1 0.499259843087283\\
2 0.622898299012219\\
3 0.674826316443923\\
4 0.704885883418512\\
5 0.724743047954077\\
6 0.739362310108021\\
7 0.750958468949473\\
8 0.759691727460227\\
9 0.767110409997124\\
10 0.772950627205378\\
11 0.77821974880641\\
12 0.782371417630688\\
13 0.785957199444241\\
14 0.496642960921615\\
15 0.60159169468312\\
16 0.650742962980057\\
17 0.680446177675622\\
18 0.700607870533534\\
19 0.715636489625572\\
20 0.727415244578511\\
};
\end{axis}
\draw[thick,red,decorate,decoration={brace,amplitude=12pt}] ($(current
axis.south east)-(0,12pt)$) -- ($(current axis.south west)-(0,12pt)$) node[midway, below,yshift=-12pt,]{Test};
\end{tikzpicture}%
\end{document}