yes forum posting increase traffic.

yes, forum posting is helpful to increase backlink and traffic on your website

I read that Forum posting will definitely increase the trafic, but how can I check if it is true ?

As long as you don't use one-liner (which will get you banned) and earnestly trying to help people, then people will surely thanked you and some even click on your link if your answer is useful enough.

By posting your content and questions on forum you can get back-links to your blog OR website in very short periods.