diff --git a/composer.json b/composer.json
index 1a036a8..8afd19e 100644
--- a/composer.json
+++ b/composer.json
@@ -14,7 +14,8 @@
     },
     "require-dev": {
         "phpunit/phpunit": "~5.0",
-        "mockery/mockery": "~0.9"
+        "mockery/mockery": "~0.9",
+        "phpunit/php-code-coverage": "^4.0"
     },
     "autoload": {
         "psr-4": {