1. Open project simple.pro.
   It's in tests\manual\debugger\simple\simple.pro of Creator's repository.
2. Uncomment the call to qthread::testQThread()
3. Place a breakpoint in qthread::Thread::run()
   I have it in line 4303:

   int j = 2;
   

4. Start debugging.
5. When the breakpoint was hit for the first time, expand "this" in the Locals view.
6. Continue.
7. Each time the breakpoint is hit, let the debugger continue and count how often you do so.
   I usually have to continue 15 or 16 times, although only 14 threads are run. In the Locals view I can see that the breakpoint is hit twice in some threads.

The debugger should hit the breakpoint exactly once for each of the threads.