Skip mcrypt-related testcases on PHP 7.1

ext/mcrypt is deprecated and the test cases in question trigger E_DEPRECATED messages as a result.
diff --git a/tests/codeigniter/libraries/Encrypt_test.php b/tests/codeigniter/libraries/Encrypt_test.php
index ced7633..adbca31 100644
--- a/tests/codeigniter/libraries/Encrypt_test.php
+++ b/tests/codeigniter/libraries/Encrypt_test.php
@@ -10,6 +10,10 @@
 		{
 			return;
 		}
+		elseif (version_compare(PHP_VERSION, '7.1.0-alpha', '>='))
+		{
+			return $this->markTestSkipped('ext/mcrypt is deprecated since PHP 7.1 and will generate notices here.');
+		}
 
 		$this->encrypt = new Mock_Libraries_Encrypt();
 		$this->ci_instance_var('encrypt', $this->encrypt);
@@ -72,4 +76,4 @@
 		$this->assertEquals('cfb', $this->encrypt->get_mode());
 	}
 
-}
\ No newline at end of file
+}
diff --git a/tests/codeigniter/libraries/Encryption_test.php b/tests/codeigniter/libraries/Encryption_test.php
index cbcae31..96e52ad 100644
--- a/tests/codeigniter/libraries/Encryption_test.php
+++ b/tests/codeigniter/libraries/Encryption_test.php
@@ -240,6 +240,10 @@
 		{
 			return $this->markTestSkipped('Cannot test MCrypt because it is not available.');
 		}
+		elseif (version_compare(PHP_VERSION, '7.1.0-alpha', '>='))
+		{
+			return $this->markTestSkipped('ext/mcrypt is deprecated since PHP 7.1 and will generate notices here.');
+		}
 
 		$this->assertTrue(is_resource($this->encryption->__driver_get_handle('mcrypt', 'rijndael-128', 'cbc')));
 	}
@@ -274,6 +278,10 @@
 			$this->markTestSkipped('Both MCrypt and OpenSSL support are required for portability tests.');
 			return;
 		}
+		elseif (version_compare(PHP_VERSION, '7.1.0-alpha', '>='))
+		{
+			return $this->markTestSkipped('ext/mcrypt is deprecated since PHP 7.1 and will generate notices here.');
+		}
 
 		$message = 'This is a message encrypted via MCrypt and decrypted via OpenSSL, or vice-versa.';
 
@@ -377,4 +385,4 @@
 		$this->assertEquals('stream', $this->encryption->mode);
 	}
 
-}
\ No newline at end of file
+}