Fix byte-safety issues & actually test for them
diff --git a/composer.json b/composer.json
index 64d1be1..0a898d2 100644
--- a/composer.json
+++ b/composer.json
@@ -17,6 +17,7 @@
 		"paragonie/random_compat": "Provides better randomness in PHP 5.x"
 	},
 	"require-dev": {
-		"mikey179/vfsStream": "1.1.*"
+		"mikey179/vfsStream": "1.1.*",
+		"phpunit/phpunit": "4.* || 5.*"
 	}
-}
\ No newline at end of file
+}