How to make the part of the rectangle wider than the red part in tikz?

Question

I have a figure where there is a train-test split visible. However, I would like to make the red part 'wider' than the blue part, but I cannot find an option in shapes.multipart that allows me to do this?

\documentclass{article}
\usepackage{graphicx}
\usepackage{tikz}
\usetikzlibrary{shapes.multipart}
\begin{document}
\tikzset{
state/.style={
       rectangle split,
       rectangle split parts=2,
       rectangle split part fill={blue!30,red!20},
       rounded corners,
       rectangle split horizontal,
       draw=black, thick,
       minimum height=6em,
       text width=0.8cm,
       minimum width=1.5em,
       inner sep=2pt,
       text centered,
       fill opacity=0.5
       }
}
\begin{figure}
    \centering
    \begin{tikzpicture}
    \node [state] at (0,0) {Train \nodepart{two} Test } ;
    \end{tikzpicture}
    \caption{Caption}
    \label{fig:my_label}
\end{figure}
\end{document}