%% test-errors.tex
%% ===============
%% The errors of subcaptionlite.  Run with -interaction=nonstopmode and
%% select the case by \CASE:
%%
%%   pdflatex -interaction=nonstopmode -jobname=test-errors-outside \
%%     "\def\CASE{outside}\input test-errors"
%%
%% Cases and the error message to find in the log:
%%   outside  \subcaption outside a float:
%%            "\subcaption outside float"
%%   type     \subcaption in a float type without subcaptions (a float
%%            "listing" defined with \@float):
%%            "Float type `listing' has no subcaptions"
\ifdefined\CASE\else\def\CASE{outside}\fi
\documentclass{article}
\usepackage{subcaptionlite}
\makeatletter
\newcounter{listing}
\def\fps@listing{tbp}
\def\ftype@listing{4}
\def\ext@listing{lol}
\def\fnum@listing{Listing~\thelisting}
\newenvironment{listing}{\@float{listing}}{\end@float}
\makeatother
\def\SCLcase#1{\def\SCLtmp{#1}\ifx\SCLtmp\CASE}
\begin{document}
\SCLcase{outside}
  \subcaption{Outside a float}
\fi
\SCLcase{type}
  \begin{listing}
    \subcaptionbox{In a listing}{Text}
    \caption{A listing}
  \end{listing}
\fi
Text.
\end{document}