Enable test again

Makefile

@@ -16,7 +16,7 @@ install: scroll
 
 test: scroll ptty
 	# check usage
-	#if ./ptty ./scroll; then exit 1; fi
+	if ./ptty ./scroll -h; then exit 1; fi
 	# check exit passthrough of child
 	if ! ./ptty ./scroll true;  then exit 1; fi
 	if   ./ptty ./scroll false; then exit 1; fi