function computeRotationAndTest(index) {
    it('#setRotationMatrix: rotate the incoming stream using direction [' +
           sphericalDirections[index] + '].',
       function(done) {
         hoaRotator.setRotationMatrix3(generateRotationMatrix(
             sphericalDirections[index][0], sphericalDirections[index][1]));
         expectedValues = sphericalHarmonicsPerDirection[index];
         context.startRendering().then(function(renderedBuffer) {
           var vectorNomal = 0;
           var numberOfChannels = renderedBuffer.numberOfChannels;
           for (var channel = 0; channel < numberOfChannels; ++channel) {
             var channelData = renderedBuffer.getChannelData(channel);
             for (var i = 0; i < channelData.length; ++i)
               vectorNomal +=
                   Math.abs(channelData[i] - expectedValues[channel]);
           }
           vectorNomal /= renderedBuffer.getChannelData(0).length *
               renderedBuffer.numberOfChannels * vectorMagnitude;
           expect(vectorNomal).to.be.below(THRESHOLD);
           done();
         });
       });
  }
TODO: describe this test.
@param {Function} done Test runner callback.
@param {Number} index Direction idex.