public Set<MessageOutput> getMessageOutputs() {
        return ImmutableSet.<MessageOutput>builder()
                .addAll(runningMessageOutputs.asMap().values())
                .add(defaultMessageOutput)
                .build();
    }
@Test
    public void testMessageOutputsIncludesDefault() {
        Set<MessageOutput> outputs = registry.getMessageOutputs();
        assertSame("we should only have the default MessageOutput", Iterables.getOnlyElement(outputs, null), messageOutput);
    }