### Question:
PendingFederation { public List<UldECKey> getPublicKeys() { return publicKeys; } PendingFederation(List<UldECKey> publicKeys); List<UldECKey> getPublicKeys(); boolean isComplete(); PendingFederation addPublicKey(UldECKey key); Federation buildFederation(Instant creationTime, long blockNumber, NetworkParameters uldParams); @Override String toString(); @Override boolean equals(Object other); Keccak256 getHash(); @Override int hashCode();  }### Answer:
@Test public void publicKeysImmutable() { boolean exception = false; try { pendingFederation.getPublicKeys().add(UldECKey.fromPrivate(BigInteger.valueOf(1000))); } catch (Exception e) { exception = true; } Assert.assertTrue(exception); exception = false; try { pendingFederation.getPublicKeys().remove(0); } catch (Exception e) { exception = true; } Assert.assertTrue(exception); }