title: Verify no exceptions were thrown in Spock
body: <p>I am brand new to Spock and perused their online docs. I have a test case where I need to verify that my fixture's interaction with a non-mock collaborator does <em>not</em> produce an exception:</p>
  
  <pre><code>class FizzSpec extends Specification {
      def "no exception thrown when we hail buzz"() {
          given:
          Fizz fixture = new Fizz()
          Buzz buzz = new Buzz("YES", true, "Garble barb") // A non-mock!
  
          when:
          fixture.hail(buzz)
  
          // TODO: How to verify the hail didn't produce an exception?
          // then:
          // thrown() == null
      }
  }
  </code></pre>
  
  <p>Any ideas as to how I can accomplish this?</p>