title: Force reinterpret_cast to return nullptr
body: <p>I'm creating unit test for a function that receives a memory address as an <code>unsigned long</code></p>
  <p>Inside the function, this addres is <code>reinterpret_cast</code>ed into a pointer of one of ur  classes.</p>
  <pre><code>void my function(Address inputAdress ) // Address comes from: typedef unsigned long Address;
  {
    ClsMyClassThread* ptr = reinterpret_cast&lt;ClsMyClassThread*&gt;(inputAdress);
  
    if(ptr == nullptr)
    {
      // Do something 
    }
  }
  </code></pre>
  <p>This function works well, but when creating the UnitTest for it, I can't figure out how can I force <code>ptr</code> to be <code>nullptr</code> (I want to test full coverage). When can this happen? Is that even posible?</p>
  <p>Thanks!</p>