public long getLastSnapshotIndex() {
        this.lock.lock();
        try {
            return this.lastSnapshotIndex;
        } finally {
            this.lock.unlock();
        }
    }
@Test
    public void testGetLastSnapshotIndex() throws Exception {
        assertEquals(this.snapshotStorage.getLastSnapshotIndex(), lastSnapshotIndex);
        assertEquals(1, this.snapshotStorage.getRefs(this.lastSnapshotIndex).get());
    }