title: Accessing inputs and outputs in sub-modules from testbench
body: <p>My device-under-test (DUT) has many sub-modules and I would like to test some of them. </p>
  
  <p>My test fixture will be the top level of my project - one level higher than the DUT - and since I can only seem to access the inputs and outputs of the modules one level down, I can only access the top-level inputs and outputs of the DUT.</p>
  
  <p>I would like to be able to access signals from the modules two or more levels beneath the test fixture, ideally without having to rewrite any modules to add more outputs so the signals I want to test are connected to the top level. </p>
  
  <p>I <em>could</em> rewrite the device under test but this seems time-consuming and I feel there should be a quicker way. </p>
  
  <p><strong>Is there a way to write a test fixture that can access signals within sub-modules, without rewriting the DUT?</strong></p>