public void Long_Running_Test()
 {
     string hash;
     const int iterations = 1000;
     var sw= new Stopwatch();
     sw.Start();
     for (var i=0; i < iterations; i++)
     {
         hash = LowPasswordHasher.HashPassword(Constants.SecurePassword);
     }
     sw.Stop();
     var low = sw.ElapsedMilliseconds/iterations;
     sw.Reset();
     sw.Start();
     for (var i = 0; i < iterations; i++)
     {
         hash = MediumPasswordHasher.HashPassword(Constants.SecurePassword);
     }
     sw.Stop();
     var medium = sw.ElapsedMilliseconds / iterations;
     sw.Reset();
     sw.Start();
     for (var i = 0; i < iterations; i++)
     {
         hash = HighPasswordHasher.HashPassword(Constants.SecurePassword);
     }
     sw.Stop();
     var high = sw.ElapsedMilliseconds / iterations;
     Assert.That(high >medium);
 }