title: Can I undo NSubstitute's Returns() substitution without recreating the mock?
body: <p>Using NSubstitute, I can do this:</p>
  
  <pre><code>mock.doStuff().Returns(foo);
  </code></pre>
  
  <p>But for a large test fixture, this isn't appropriate in every test.</p>
  
  <p>So can I "undo" that <code>Returns()</code> substitution, or must I recreate the mock before each test? (which is slooooow...)</p>