Counts the number of nodes in a document to allow assertions to be made
using a NodeTest.
Examples and more at xmlunit.sourceforge.net
See Also:NodeTest
Called by NodeTest when all nodes have been iterated over: time to see
if all the nodes that were expected were found.
Note that this method also invokes
CountingNodeTester.resetCounter resetCounter so that the instance can be reused.
true if expected num nodes == actual num nodes,false otherwise