MergeConfigurationSource implements ConfigurationSource { @Override public void init() { for (ConfigurationSource source : sources) { source.init(); } } MergeConfigurationSource(ConfigurationSource... sources); @Override Properties getConfiguration(Environment environment); @Override void init(); @Override String toString();  }
@Test void initInitializesAllSources() { for (ConfigurationSource underlyingSource : underlyingSources) { verify(underlyingSource, atLeastOnce()).init(); } }