* Make sure all 'nodes' are unique.
* @throws Exception
*/
public void testUniqueNodes() throws Exception {
Document gmfgraph = getGmfgraph();
IterableElementList nl = xpath(gmfgraph, "/Canvas/nodes");
assertNotSame("We should have at least one node node", nl.getLength(), 0);
Set<String> found = new HashSet<String>();
for (Element child : nl) {
String childName = child.getAttribute("name");
assertFalse("More than one node found for '" + childName + "'", found.contains(childName));