@Override
    public String toString() {
        return "PartitionAssignment" +
                "(replicas=" + replicas +
                ", directories=" + directories +
                ")";
    }
@Test
    public void testToString() {
        List<Integer> replicas = Arrays.asList(0, 1, 2);
        List<Uuid> directories = Arrays.asList(
                Uuid.fromString("65WMNfybQpCDVulYOxMCTw"),
                Uuid.fromString("VkZ5AkuESPGkMc2OxpKUjw"),
                Uuid.fromString("wFtTi4FxTlOhhHytfxv7fQ")
        );
        PartitionAssignment partitionAssignment = new PartitionAssignment(replicas, directories::get);
        assertEquals("PartitionAssignment(replicas=[0, 1, 2], " +
                "directories=[65WMNfybQpCDVulYOxMCTw, VkZ5AkuESPGkMc2OxpKUjw, wFtTi4FxTlOhhHytfxv7fQ])", partitionAssignment.toString());
    }