@Test
public void testListGraphNodes() {

	final int nodesToTry = 50;
	final HexTable index = new HexTable();
	final Set<Node> graphNodes = new HashSet<>(nodesToTry);
	index.begin(null);
	for (int i = 0; i < nodesToTry; i++) {
		final Node node = createBlankNode();
		index.add(Quad.create(node, node, node, node));
		graphNodes.add(node);
		assertEquals(graphNodes, index.listGraphNodes().collect(toSet()));
	}
	index.end();
}