96 GMC Sierra 3500 Clicks won't turn over.

My work truck, 96 Sierra 3500 Pickup clicks but won't even turn over. It has been sitting for a few weeks. Battery is brand new and lights are bright.
I'm guessing it's the starter. Any way to diagnose the starter to be sure? I guess the solenoid in the starter clicks but the truck still won't turn over. Would tapping on the starter help it to start? It never showed any problems with starting before.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
You need to check the cables where they hook to the battery.

has
sure?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.