diff --git a/tests/Base64UrlSafeTest.php b/tests/Base64UrlSafeTest.php
index a41bf1e..136ed61 100644
--- a/tests/Base64UrlSafeTest.php
+++ b/tests/Base64UrlSafeTest.php
@@ -1,11 +1,19 @@
 <?php
-use \ParagonIE\ConstantTime\Base64UrlSafe;
 
+use ParagonIE\ConstantTime\Base64UrlSafe;
+use ParagonIE\ConstantTime\Binary;
+
+/**
+ * Class Base64UrlSafeTest
+ */
 class Base64UrlSafeTest extends PHPUnit\Framework\TestCase
 {
     /**
      * @covers Base64UrlSafe::encode()
      * @covers Base64UrlSafe::decode()
+     *
+     * @throws Exception
+     * @throws TypeError
      */
     public function testRandom()
     {
@@ -34,5 +42,17 @@ public function testRandom()
                 );
             }
         }
+
+        $random = \random_bytes(1 << 20);
+        $enc = Base64UrlSafe::encode($random);
+        $this->assertTrue(Binary::safeStrlen($enc) > 65536);
+        $this->assertSame(
+            $random,
+            Base64UrlSafe::decode($enc)
+        );
+        $this->assertSame(
+            \strtr(\base64_encode($random), '+/', '-_'),
+            $enc
+        );
     }
 }