Add unit test for RSA cipher (#3664)

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

@@ -0,0 +1,24 @@
+package com.thealgorithms.ciphers;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+class RSATest {
+
+    RSA rsa = new RSA(1024);
+
+    @Test
+    void testRSA() {
+        // given
+        String textToEncrypt = "Such secure";
+
+        // when
+        String cipherText = rsa.encrypt(textToEncrypt);
+        String decryptedText = rsa.decrypt(cipherText);
+
+        // then
+        assertEquals("Such secure", decryptedText);
+    }
+
+}