### Question:
KeyPair { public PrivateKey getPrivateKey() { return new PrivateKey(secretKey); } KeyPair();  KeyPair(byte[] seed);  KeyPair(String secretKey, Encoder encoder); PublicKey getPublicKey(); PrivateKey getPrivateKey();  }### Answer:
@Test public void testPrivateKeyToString() throws Exception { try { KeyPair key = new KeyPair(HEX.decode(BOB_SEED)); assertEquals("Correct private key expected", BOB_ENCRYPTION_PRIVATE_KEY, key.getPrivateKey().toString()); } catch (Exception e) { fail("Should return a valid key size"); } }