verify that resolve_theme_file with no arguments resolves built-in default theme
verify that resolve_theme_file with no arguments resolves built-in default theme

asciidoctor/asciidoctor-pdf,Hextremist/asciidoctor-pdf,mojavelinux/asciidoctor-pdf,Hextremist/asciidoctor-pdf,asciidoctor/asciidoctor-pdf,mojavelinux/asciidoctor-pdf,dsisnero/asciidoctor-pdf,dsisnero/asciidoctor-pdf