title: Checking for a throw new Error with should.js and Mocha
body: <p>I've got an error thrown like so:</p>
  
  <pre><code>if (somethingBadHappened) {
      throw new Error('what were you thinking, batman?')
  }
  </code></pre>
  
  <p>Now I want to write a test to check that this throws when expected:</p>
  
  <pre><code>should(MyClass.methodThatShouldThrow()).throws('what were you thinking, batman?')
  </code></pre>
  
  <p>But that actually throws the error. What am I doing wrong? Should.js docs are pretty light, since it inherits from <code>assert.throws</code>, but even the docs for that doesn't work in the 'should.js' way?</p>