title: how do you assert an exception from another ruby module is thrown? (using assert_throws)
body: <p>I'm trying to write code like this:</p>
  
  <pre><code>assert_throws(:ExtractionFailed) { unit.extract_from('5 x 2005')}
  </code></pre>
  
  <p><code>ExtractionFailed</code> is a trivial subclass of <code>Exception</code>, and under test/unit, I'm trying to assert that it is thrown when I call unit.extract_from(... bad data...) </p>
  
  <p>I've moved <code>ExtractionFailed</code> into the SemanticText module, so now test/unit says:</p>
  
  <pre><code>&lt;:ExtractionFailed&gt; expected to be thrown but
  &lt;:"SemanticText::ExtractionFailed"&gt; was thrown.
  </code></pre>
  
  <p>I tried writing assert_throws(:SemanticText::ExtractionFailed) {...} but I got the rather confusing message: <code>TypeError: SemanticText is not a class/module</code></p>
  
  <p>I can make it work by doing the following (although it seems like a hack):</p>
  
  <pre><code>  assert_throws(SemanticText::ExtractionFailed.to_s.to_sym) { unit.extract_from('5 x 2005')}
  </code></pre>
  
  <p>So what's the right way to say this assertion in ruby?</p>