code: function runHighland(deferred, highlandStream) {
    highlandStream.pull(function(err, z) {
      if(err) {
        deferred.reject(err);
        return;
      }
  
      deferred.resolve(z);
    });
  }
docs: Using pull() seems to give the fastest results for highland, but will only work for test runs that reduce a stream to a single value.