message: Updated test_util.cc
  Fixed warning of comparison
diff: @@ -124,7 +124,7 @@ void SingleOpModel::BuildInterpreter(std::vector<std::vector<int>> input_shapes,
  CHECK(interpreter_ != nullptr);
  - for (int i = 0; i < input_shapes.size(); ++i) {
  + for (size_t i = 0; i < input_shapes.size(); ++i) {
  const int input_idx = interpreter_->inputs()[i];
  if (input_idx == kOptionalTensor) continue;
  const auto& shape = input_shapes[i];
  