Do you have a trailer brake hooked up in your truck ?(looks like a radar detector .)
You should ,and when you ajust it you can tell if brakes are working.
I have one like this ,you put the % of braking you would like.
I like 15% around town and trafic and usually run at 20% on long trips with no stoping.
It also brakes when stopping sharply to what ever it needs up to a panic lockup.