### Question:
AesEncryptor implements Encryptor { @Override public String encrypt(String value) { return encrypt(value, null); } AesEncryptor();  AesEncryptor(String key); @Override String encrypt(String value); @Override String encrypt(String value, byte[] iv); @Override String decrypt(String value); @Override String decrypt(String value, byte[] iv); @Override void setKey(String key);  }### Answer:
@Test public void testEncryptionForNullString() { Encryptor encryptor = new AesEncryptor(); String b64Encrypted = encryptor.encrypt(null); assertNull(b64Encrypted); }