when(outputService.load(eq(outputId))).thenReturn(output);
final OutputRegistry outputRegistry = new OutputRegistry(null, outputService, messageOutputFactory);
assertEquals(outputRegistry.getRunningMessageOutputs().size(), 0);
MessageOutput result = outputRegistry.getOutputForId(outputId);
assertSame(result, messageOutput);
assertNotNull(outputRegistry.getRunningMessageOutputs());
assertEquals(outputRegistry.getRunningMessageOutputs().size(), 1);
verify(result).initialize(any(Configuration.class));