Add ADFGVX Cipher (#5631)

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

@@ -0,0 +1,36 @@
+package com.thealgorithms.ciphers;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+class ADFGVXCipherTest {
+
+    ADFGVXCipher adfgvxCipher = new ADFGVXCipher();
+
+    @Test
+    void adfgvxCipherEncryptTest() {
+        // given
+        String message = "attack at 1200am"; // Plaintext message
+        String keyword = "PRIVACY";
+
+        // when
+        String cipherText = adfgvxCipher.encrypt(message, keyword);
+
+        // then
+        assertEquals("DGDDDAGDDGAFADDFDADVDVFAADVX", cipherText);
+    }
+
+    @Test
+    void adfgvxCipherDecryptTest() {
+        // given
+        String cipherText = "DGDDDAGDDGAFADDFDADVDVFAADVX"; // Ciphertext message
+        String keyword = "PRIVACY";
+
+        // when
+        String plainText = adfgvxCipher.decrypt(cipherText, keyword);
+
+        // then
+        assertEquals("ATTACKAT1200AM", plainText);
+    }
+}