Add Junit tests for AESEncryption.java (#5597)

src/test/java/com/thealgorithms/ciphers/AESEncryptionTest.java

@@ -0,0 +1,62 @@
+package com.thealgorithms.ciphers;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import javax.crypto.SecretKey;
+import org.junit.jupiter.api.Test;
+
+public class AESEncryptionTest {
+
+    @Test
+    public void testGetSecretEncryptionKey() throws Exception {
+        SecretKey key = AESEncryption.getSecretEncryptionKey();
+        assertNotNull(key, "Secret key should not be null");
+        assertEquals(128, key.getEncoded().length * 8, "Key size should be 128 bits");
+    }
+
+    @Test
+    public void testEncryptText() throws Exception {
+        String plainText = "Hello World";
+        SecretKey secKey = AESEncryption.getSecretEncryptionKey();
+        byte[] cipherText = AESEncryption.encryptText(plainText, secKey);
+
+        assertNotNull(cipherText, "Ciphertext should not be null");
+        assertTrue(cipherText.length > 0, "Ciphertext should not be empty");
+    }
+
+    @Test
+    public void testDecryptText() throws Exception {
+        String plainText = "Hello World";
+        SecretKey secKey = AESEncryption.getSecretEncryptionKey();
+        byte[] cipherText = AESEncryption.encryptText(plainText, secKey);
+
+        // Decrypt the ciphertext
+        String decryptedText = AESEncryption.decryptText(cipherText, secKey);
+
+        assertNotNull(decryptedText, "Decrypted text should not be null");
+        assertEquals(plainText, decryptedText, "Decrypted text should match the original plain text");
+    }
+
+    @Test
+    public void testEncryptDecrypt() throws Exception {
+        String plainText = "Hello AES!";
+        SecretKey secKey = AESEncryption.getSecretEncryptionKey();
+
+        // Encrypt the plaintext
+        byte[] cipherText = AESEncryption.encryptText(plainText, secKey);
+
+        // Decrypt the ciphertext
+        String decryptedText = AESEncryption.decryptText(cipherText, secKey);
+
+        assertEquals(plainText, decryptedText, "Decrypted text should match the original plain text");
+    }
+
+    @Test
+    public void testBytesToHex() {
+        byte[] bytes = new byte[] {0, 1, 15, 16, (byte) 255}; // Test with diverse byte values
+        String hex = AESEncryption.bytesToHex(bytes);
+        assertEquals("00010F10FF", hex, "Hex representation should match the expected value");
+    }
+}