old_contents: 
  /**
   * Module dependencies.
   */
  
  var stylus = require('stylus'),
      nib = require('../'),
      fs = require('fs');
  
  // test cases
  
  var cases = fs.readdirSync('test/cases').filter(function(file){
    return ~file.indexOf('.styl');
  }).map(function(file){
    return file.replace('.styl', '');
  });
  
  describe('integration', function(){
    cases.forEach(function(test){
      var name = test.replace(/[-.]/g, ' ');
      it(name, function(){
        var path = 'test/cases/' + test + '.styl';
        var styl = fs.readFileSync(path, 'utf8').replace(/\r/g, '');
        var css = fs.readFileSync('test/cases/' + test + '.css', 'utf8').replace(/\r/g, '').trim();
  
        var style = stylus(styl)
          .use(nib())
          .set('filename', path)
          .define('url', stylus.url());
  
        if (~test.indexOf('compress')) style.set('compress', true);
  
        style.render(function(err, actual){
          if (err) throw err;
          actual.trim().should.equal(css);
        });
      });
    });
  });
  
new_contents: /**
   * Module dependencies.
   */
  var stylus = require('stylus'),
      nib = require('../'),
      fs = require('fs');
  
  /**
   * Read test/cases directory and filter all `.styl` files, then remove
   * this extension for each file in the collection and prepare to test.
   */
  var cases = fs.readdirSync('test/cases').filter(function(file){
    return ~file.indexOf('.styl'); // bitwise flip to treat result as truthy.
  }).map(function(file){
    return file.replace('.styl', '');
  });
  
  /*
   * For each `.styl` and `.css` pair in `test/cases`, compile stylus to css
   * and compare actual result to expected css.
   */
  describe('integration', function(){
    cases.forEach(function(test){
      var name = test.replace(/[-.]/g, ' ');
      it(name, function(){
        var path = 'test/cases/' + test + '.styl';
        var styl = fs.readFileSync(path, 'utf8').replace(/\r/g, '');
        var css = fs.readFileSync('test/cases/' + test + '.css', 'utf8').replace(/\r/g, '').trim();
  
        var style = stylus(styl)
          .use(nib())
          .set('filename', path)
          .define('url', stylus.url());
  
        if (~test.indexOf('compress')) style.set('compress', true);
  
        style.render(function(err, actual){
          if (err) throw err;
          actual.trim().should.equal(css);
        });
      });
    });
  });
  
subject: improve comments for test runner