@Test
  public void testCheckForExpiredSSTableBlockers() throws InterruptedException {
    String KEYSPACE1 = "Keyspace1";
    ColumnFamilyStore cfs = Keyspace.open("Keyspace1").getColumnFamilyStore("Standard1");
    cfs.truncateBlocking();
    cfs.disableAutoCompaction();
    cfs.metadata.gcGraceSeconds(0);

    RowMutation rm = new RowMutation(KEYSPACE1, Util.dk("test").key);
    rm.add(
        "Standard1",
        ByteBufferUtil.bytes("col1"),
        ByteBufferUtil.EMPTY_BYTE_BUFFER,
        System.currentTimeMillis());
    rm.applyUnsafe();
    cfs.forceBlockingFlush();
    SSTableReader blockingSSTable = cfs.getSSTables().iterator().next();
    for (int i = 0; i < 10; i++) {
      rm = new RowMutation(KEYSPACE1, Util.dk("test").key);
      rm.delete("Standard1", System.currentTimeMillis());
      rm.applyUnsafe();
      cfs.forceBlockingFlush();
    }
    Multimap<SSTableReader, SSTableReader> blockers =
        SSTableExpiredBlockers.checkForExpiredSSTableBlockers(
            cfs.getSSTables(), (int) (System.currentTimeMillis() / 1000) + 100);
    assertEquals(1, blockers.keySet().size());
    assertTrue(blockers.keySet().contains(blockingSSTable));
    assertEquals(10, blockers.get(blockingSSTable).size());
  }