def compare_files(self, files, ref_subdir="."):
        """Check some files in the work root match those in the ref directory

        The files argument gives the list of files to check. These are
        interpreted as paths relative to the work directory and relative to
        self.ref_dir / ref_subdir.

        This is a wrapper around edalize_common.compare_files: see its
        documentation for how to use the :envvar:`GOLDEN_RUN` environment
        variable to copy across a golden reference.

        """
        ref_dir = os.path.normpath(os.path.join(self.ref_dir, ref_subdir))
        return compare_files(ref_dir, self.work_root, files)