Exactly you can if you want to - we all have a choice if we take quick acting insulin to calculate the carbs and take the insulin.
However for me personally there's a few other things I have to consider first, so if I test first and any higher than 9mmol/l then I will then decide if I want to wait until i'm back below 7 mmol/l before having a treat, then if I do want the treat I tend to bolus 20 minutes beforehand to try and avoid the spike, my personal issue is that if I run higher than 12 mmol/l then I have to take a higher bolus to correct.. and so ultimately is it worth it, and that's the point where I generally decline the offer