documentclass[]{article}
usepackage{pstool}

begin{document}
    begin{figure}[ht]
        psfragfig*[width=1textwidth]{imx/testfig}{
            psfrag{INP}{Test}
        }
    end{figure}
end{document}

usepackage[cleanup={.dvi, .ps, .pdf, .log}]{pstool}
% temporary .tex files are not deleted

% pstool.sty
...
IfFileExists{#2.tex}{%
  edefpstool@tex{#2.tex}%
}{%
  letpstool@tex@empty
  PackageWarning{pstool}{%
    No file "#2.tex" or "#2-psfrag.tex" can be found
    that may contain macros for "pstool@eps.eps"%
  }%
}%
...