feat(manifest): allow test verb without path argument

src/cli/Manifest.vala

@@ -22,7 +22,7 @@ public static int manifest_main(string[] args) {
                 build_path = args[i];
             }
         }
-    } else if(verb != "remove" && verb != "acquire" && verb != "install" && verb != "package") {
+    } else if(verb != "remove" && verb != "acquire" && verb != "install" && verb != "package" && verb != "test") {
         if(args.length < 3) {
             manifest_usage();
             return 255;