### Question:
SimpleKeyCryptoBuilder extends KeyCryptoBuilder { @Override public KeyCryptoBuilder setServerAddress(final URI serverAddress) { if (serverAddress == null) { throw new NullPointerException("Server address cannot be null."); } this.serverAddress = serverAddress; markAsSet(Attribute.SERVER_ADDRESS); return this; }  @Override KeyCryptoProduct build(); @Override KeyCryptoBuilder setKeySalt(final String keySalt); @Override KeyCryptoBuilder setPrivateKey(final URI privateKey); @Override KeyCryptoBuilder setServerAddress(final URI serverAddress); @Override KeyCryptoBuilder setUsername(final String username);  }### Answer:
@Test(expected = NullPointerException.class) public void testNullServerAddress() { builder.setServerAddress(null); }