@Test
  public void extensionsWithAnnotatedOptions() {
    ExtensionWithAnnotatedOptions extension = new ExtensionWithAnnotatedOptions();

    // Ensure default annotation support works
    assertThat(extension.getSupportedOptions()).contains(CUSTOM_OPTION);

    // Ensure it's carried over to the AutoValue processor
    assertThat(new AutoValueProcessor(ImmutableList.of(extension)).getSupportedOptions())
        .contains(CUSTOM_OPTION);
  }
Tests that extensions providing their own (annotated) annotation types or options get picked
up.
value/src/test/java/com/google/auto/value/processor/ExtensionTest.java