diff --git a/composer.json b/composer.json
index 7786a64..937d349 100644
--- a/composer.json
+++ b/composer.json
@@ -9,7 +9,8 @@
         "silverstripe-themes/simple": "~3.2.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "^5.7"
+        "phpunit/phpunit": "^5.7",
+        "sminnee/phpunit-mock-objects": "^3.4.5"
     },
     "extra": {
         "project-files": [
@@ -27,4 +28,4 @@
     },
     "prefer-stable": true,
     "minimum-stability": "dev"
-}
\ No newline at end of file
+}