code: function exist(_super) {
      return function() {
        var obj = this._obj;
        if (obj instanceof FileHelper || obj instanceof DirectoryHelper) {
          var ssf = utils.flag(this, 'ssfi');
  
          if (utils.flag(this, 'negate')) {
            obj.assertDoesNotExist(ssf);
          } else {
            obj.assertExists(ssf);
          }
  
        } else {
          _super.call(this);
        }
      };
    }
docs: ### .exist
  
  Asserts that a file or directory exists.
  
  expect(file('index.js')).to.exist;
  expect(file('index.coffee')).to.not.exist;
  
  expect(dir('foo')).to.exist;
  expect(dir('missing')).to.not.exist;
  
  @name exist
  @namespace BDD
  @api public