I eventually found a unit test which takes more than 3 seconds on my machine: HashRingTest::testHashRingKetamaMode. It has been introduced in f2e6543c46fff5ce43839982ecd56ebcc10f4d62 by @aaron
It does compute a hashring for 100 nodes as far as I can understand. Would be nice to make it faster, we probably do not need to compute the ring for 100 nodes?