@Test
public void testReplaceContainer() throws Exception {
config.newTransaction().addContainer(EXTRA_CONTAINER).commit();
ConfigObserver observer = EasyMock.createMock(ContainerConfig.ConfigObserver.class);
observer.containersChanged(EasyMock.isA(ContainerConfig.class),
EasyMock.eq(ImmutableSet.of("extra")), EasyMock.eq(ImmutableSet.<String>of()));
EasyMock.replay(observer);
config.addConfigObserver(observer, false);
config.newTransaction().addContainer(MODIFIED_EXTRA_CONTAINER).commit();