2
You do not search for .else, but for .unknown (see section 82.3.6 in the TikZ manual).
\documentclass[tikz,border=7pt]{standalone}
\tikzset{
test/.is choice,
test/1/.style={red},
test/2/.style={blue},
test/.unknown/.style={yellow}
}
\begin{document}
\begin{tikzpicture}
\fill[test=1...