fix mono alphabetic cipher test structure

Author: salehhashemi1992

Diff for: tests/Ciphers/MonoAlphabeticCipherTest.php

@@ -2,8 +2,6 @@
 
 use PHPUnit\Framework\TestCase;
 
-use function PHPUnit\Framework\assertEquals;
-
 require_once __DIR__ . '/../../vendor/autoload.php';
 require_once __DIR__ . '/../../Ciphers/MonoAlphabeticCipher.php';
 
@@ -15,7 +13,7 @@ public function testMonoAlphabeticCipher()
         $key = "yhkqgvxfoluapwmtzecjdbsnri";
         $text = "I love1234 GitHub";
         $encryptedText = "O ambg XojFdh";
-        assertEquals(maEncrypt($key, $alphabet, $text), $encryptedText);
-        assertEquals(maDecrypt($key, $alphabet, $encryptedText), "I love GitHub");
+        $this->assertEquals(maEncrypt($key, $alphabet, $text), $encryptedText);
+        $this->assertEquals(maDecrypt($key, $alphabet, $encryptedText), "I love GitHub");
     }
 }