anchor.diff:         text:filename
       });
       $tabFilenames.append($tab);
  -    setupTabFilenameClickHandler($tab);
  +    setupFilenameTabClickHandler($tab);
     };
   
  -  const setupStdoutTab = () => {
  +  const setupOutputTab = (s) => {
       const $tab = $('<div>', {
           class: 'tab-filename',
  -         text: 'stdout'
  +           id: `radio_${s}`,
  +         text: s
       });
       $tabFilenames.append($tab);
  -    setupTabFilenameClickHandler($tab);
  +    setupFilenameTabClickHandler($tab);
     };
   
  -  const setupStderrTab = () => {
  -    const $tab = $('<div>', {
  -        class: 'tab-filename',
  -         text: 'stderr'
  +  const setupFilenameTabClickHandler = (div) => {
  +    div.click(() => {
  +      if (div.hasClass('selected')) { return; }
  +      const filename = div.text();
  +      cd.loadFile(filename);
  +      $('.tab-filename').removeClass('selected');
  +      div.addClass('selected');
       });
  -    $tabFilenames.append($tab);
  -    setupTabFilenameClickHandler($tab);
     };
  +
  +  //- - - - - - - - - - - - - - - - - - - - - - - - -
   
     const setupReplTab = () => {
       const $tab = $('<div>', {
  
positive.code:     });
      $tabFilenames.append($tab);
      setupReplTabClickHandler($tab);
    };
  
    const setupTabFilenameClickHandler = (div) => {
      div.click(() => {
        if (div.hasClass('selected')) { return; }
        const filename = div.text();
        cd.loadFile(filename);
        $('.tab-filename').removeClass('selected');
        div.addClass('selected');
      });
    };
  
    const setupReplTabClickHandler = (div) => {
  
negative.code:   };
  
    setupCurrentFilenameTab('cyber-dojo.sh');
    setupOutputTab('stdout')
    setupOutputTab('stderr')
    setupReplTab()
  
  });
  