@Override
            public ImmutableSet<? extends Element> process(
                ImmutableSetMultimap<String, Element> elementsByAnnotation) {
              generateClass(processingEnv.getFiler(), "SomeGeneratedClass");
              return ImmutableSet.of();
            }
Generates a class called {@code test.SomeGeneratedClass}.
common/src/test/java/com/google/auto/common/BasicAnnotationProcessorTest.java