@Test
public void concurrentDownload()
{

   Source source = new Source();
   Assert.assertEquals(source.concurrentDownload(), 0);
   String calculatorId = UUID.randomUUID().toString();
   Assert.assertTrue(source.generateBandwidthCalculator(calculatorId));
   Assert.assertEquals(source.concurrentDownload(), 1);
   source.removeBandwidthCalculator(calculatorId);
   Assert.assertEquals(source.concurrentDownload(), 0);
}