@Override
    protected Iterable<? extends Step> steps() {
      return ImmutableList.of(
          new Step() {
            @Override
            public ImmutableSet<? extends Element> process(
                ImmutableSetMultimap<String, Element> elementsByAnnotation) {
              generateClass(processingEnv.getFiler(), "SomeGeneratedClass");
              return ImmutableSet.of();
            }

            @Override
            public ImmutableSet<String> annotations() {
              return ImmutableSet.of(ENCLOSING_CLASS_NAME + ".GeneratesCode");
            }
          });
    }
Generates a class called {@code test.SomeGeneratedClass}.
common/src/test/java/com/google/auto/common/BasicAnnotationProcessorTest.java