OneTimePadCipherTest.java

package com.thealgorithms.ciphers;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertThrows;

import java.nio.charset.StandardCharsets;
import org.junit.jupiter.api.Test;

public class OneTimePadCipherTest {

    @Test
    public void encryptDecryptWorks() {
        String original = "OTP Test";
        byte[] plaintext = original.getBytes(StandardCharsets.UTF_8);
        byte[] key = OneTimePadCipher.generateKey(plaintext.length);

        byte[] encrypted = OneTimePadCipher.encrypt(plaintext, key);
        byte[] decrypted = OneTimePadCipher.decrypt(encrypted, key);

        assertEquals(original, new String(decrypted, StandardCharsets.UTF_8));
    }

    @Test
    public void throwsIfDifferentLength() {
        byte[] plaintext = "Hi".getBytes(StandardCharsets.UTF_8);
        byte[] key = new byte[] {1, 2, 3};

        assertThrows(
            IllegalArgumentException.class,
            () -> OneTimePadCipher.encrypt(plaintext, key)
        );
    }
}