const { ShellService } = ChromeUtils.import(
  "resource:///modules/ShellService.jsm"
);

function test() {
  ShellService.setDefaultBrowser(true, false);
  ok(
    ShellService.isDefaultBrowser(true, false),
    "we got here and are the default browser"
  );
  ok(
    ShellService.isDefaultBrowser(true, true),
    "we got here and are the default browser"
  );
}