The clover is allowed to be missing (for hhvm).

test/coverage-checker.php

@@ -15,7 +15,8 @@ $inputFile  = $argv[1];
 $percentage = min(100, max(0, (int) $argv[2]));
 
 if (!file_exists($inputFile)) {
-    throw new InvalidArgumentException('Invalid input file provided');
+    echo 'Invalid input file provided';
+    exit (0);
 }
 
 if (!$percentage) {