@Override
        public void visit(TraceNode node) {
            if (SOURCE1.equals(node.payload())) {
                traceFromSource1 = true;
            } else if (SOURCE2.equals(node.payload())) {
                traceFromSource2 = true;
            }
        }
Test for federation searcher. The searcher is also tested in
com.yahoo.prelude.searcher.test.BlendingSearcherTestCase.

@author Arne Bergene Fossaa
container-search/src/test/java/com/yahoo/search/federation/FederationSearcherTestCase.java