@Test public void rejectionOfNullMethods() {
    try {
      new EventProducer(this, null);
      fail("EventProducer must immediately reject null methods.");
    } catch (NullPointerException expected) {
      // Hooray!
    }
  }
Checks that EventProducer's constructor disallows null methods.
otto/src/test/java/com/squareup/otto/EventProducerTest.java