RSA in Java

KeyPairTest.java

class KeyPairTest {

    @Test
    void sut_correctly_encrypt_message() throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException {
        KeyPair keyPair = getKeyPair();
        PublicKey publicKey = keyPair.getPublic();

        Cipher encryptCipher = Cipher.getInstance("RSA");
        encryptCipher.init(Cipher.ENCRYPT_MODE, publicKey);
        String message = "Hello World!";

        byte[] messageBytes = message.getBytes(StandardCharsets.UTF_8);
        byte[] encrypedMessageBytes = encryptCipher.doFinal(messageBytes);

        String encodedMessage = new String(messageBytes, StandardCharsets.UTF_8);
        String encryptedMessage = new String(encrypedMessageBytes, StandardCharsets.UTF_8);

        assertThat(encodedMessage).isEqualTo(message);
        assertThat(encryptedMessage).isNotEqualTo(message);
    }

    @Test
    void sut_correctly_decrypt_message() throws NoSuchAlgorithmException, NoSuchPaddingException, InvalidKeyException, IllegalBlockSizeException, BadPaddingException {
        KeyPair keyPair = getKeyPair();
        PublicKey publicKey = keyPair.getPublic();
        PrivateKey privateKey = keyPair.getPrivate();

        Cipher encryptCipher = Cipher.getInstance("RSA");
        encryptCipher.init(Cipher.ENCRYPT_MODE, publicKey);
        String message = "Hello World!";

        byte[] messageBytes = message.getBytes(StandardCharsets.UTF_8);
        byte[] encrypedMessageBytes = encryptCipher.doFinal(messageBytes);

        Cipher decryptCipher = Cipher.getInstance("RSA");
        decryptCipher.init(Cipher.DECRYPT_MODE, privateKey);

        byte[] decryptedMessageBytes = decryptCipher.doFinal(encrypedMessageBytes);
        String decryptedMessage = new String(decryptedMessageBytes, StandardCharsets.UTF_8);

        assertThat(decryptedMessage).isEqualTo(message);
    }

    private static KeyPair getKeyPair() throws NoSuchAlgorithmException {
        KeyPairGenerator generator = KeyPairGenerator.getInstance("RSA");
        generator.initialize(2048);
        KeyPair keyPair = generator.generateKeyPair();
        return keyPair;
    }
}