diff --git a/tests/Unit/Crypt/AES/InternalTest.php b/tests/Unit/Crypt/AES/InternalTest.php
index 2a9652ca..41801c85 100644
--- a/tests/Unit/Crypt/AES/InternalTest.php
+++ b/tests/Unit/Crypt/AES/InternalTest.php
@@ -9,9 +9,8 @@ class Unit_Crypt_AES_InternalTest extends Unit_Crypt_AES_TestCase
 {
     static public function setUpBeforeClass()
     {
-        parent::setUpBeforeClass();
+        self::$engine = CRYPT_MODE_INTERNAL;
 
-        self::ensureConstant('CRYPT_AES_MODE', CRYPT_AES_MODE_INTERNAL);
-        self::ensureConstant('CRYPT_RIJNDAEL_MODE', CRYPT_RIJNDAEL_MODE_INTERNAL);
+        parent::setUpBeforeClass();
     }
 }
diff --git a/tests/Unit/Crypt/AES/McryptTest.php b/tests/Unit/Crypt/AES/McryptTest.php
index 4327c7ea..78902fc0 100644
--- a/tests/Unit/Crypt/AES/McryptTest.php
+++ b/tests/Unit/Crypt/AES/McryptTest.php
@@ -13,9 +13,8 @@ class Unit_Crypt_AES_McryptTest extends Unit_Crypt_AES_TestCase
             self::markTestSkipped('mcrypt extension is not available.');
         }
 
-        parent::setUpBeforeClass();
+        self::$engine = CRYPT_MODE_MCRYPT;
 
-        self::ensureConstant('CRYPT_AES_MODE', CRYPT_AES_MODE_MCRYPT);
-        self::ensureConstant('CRYPT_RIJNDAEL_MODE', CRYPT_RIJNDAEL_MODE_MCRYPT);
+        parent::setUpBeforeClass();
     }
 }
diff --git a/tests/Unit/Crypt/AES/TestCase.php b/tests/Unit/Crypt/AES/TestCase.php
index 91cb9792..2a40450c 100644
--- a/tests/Unit/Crypt/AES/TestCase.php
+++ b/tests/Unit/Crypt/AES/TestCase.php
@@ -9,12 +9,11 @@ require_once 'Crypt/AES.php';
 
 abstract class Unit_Crypt_AES_TestCase extends PhpseclibTestCase
 {
+    protected static $engine;
+
     static public function setUpBeforeClass()
     {
         parent::setUpBeforeClass();
-
-        self::reRequireFile('Crypt/Rijndael.php');
-        self::reRequireFile('Crypt/AES.php');
     }
 
     /**
@@ -64,6 +63,7 @@ abstract class Unit_Crypt_AES_TestCase extends PhpseclibTestCase
     public function testEncryptDecryptWithContinuousBuffer($mode, $plaintext, $iv, $key)
     {
         $aes = new Crypt_AES(constant($mode));
+        $aes->setEngine(self::$engine);
         $aes->enableContinuousBuffer();
         $aes->setIV($iv);
         $aes->setKey($key);
@@ -85,6 +85,7 @@ abstract class Unit_Crypt_AES_TestCase extends PhpseclibTestCase
         // https://web.archive.org/web/20070209120224/http://fp.gladman.plus.com/cryptography_technology/rijndael/aesdvec.zip
 
         $aes = new Crypt_Rijndael();
+        $aes->setEngine(self::$engine);
         $aes->disablePadding();
         $aes->setKey(pack('H*', '2b7e151628aed2a6abf7158809cf4f3c762e7160')); // 160-bit key. Valid in Rijndael.
         $ciphertext = $aes->encrypt(pack('H*', '3243f6a8885a308d313198a2e0370734'));
@@ -99,6 +100,7 @@ abstract class Unit_Crypt_AES_TestCase extends PhpseclibTestCase
         // same as the above - just with a different ciphertext
 
         $aes = new Crypt_AES();
+        $aes->setEngine(self::$engine);
         $aes->disablePadding();
         $aes->setKey(pack('H*', '2b7e151628aed2a6abf7158809cf4f3c762e7160')); // 160-bit key. AES should null pad to 192-bits
         $ciphertext = $aes->encrypt(pack('H*', '3243f6a8885a308d313198a2e0370734'));