edlp_d8/core/modules/system/tests/themes/test_theme_libraries_extend/test_theme_libraries_extend.libraries.yml

extend_one:
  css:
    theme:
      css/extend_1.css: { }
  js:
    js/extend_1.js: { }

extend_two:
  css:
    theme:
      css/extend_2.css: { }