@Override
	public Enumeration<String> getKeys() {
		if ( parent == null ) {
			return Collections.enumeration( contents.keySet() );
		}

		Set<String> keySet = newHashSet( contents.keySet() );
		keySet.addAll( Collections.list( parent.getKeys() ) );

		return Collections.enumeration( keySet );
	}
@Test
	public void aggregateBundleWithNoSourceBundlesContainsNoKeys() {
		ResourceBundle aggregateBundle = new AggregateResourceBundle( Collections.<ResourceBundle>emptyList() );
		assertTrue( getAsSet( aggregateBundle.getKeys() ).isEmpty() );
	}