@Test
    void testBlendingFederationWithGrouping() {
        DocumentSourceSearcher docSource1 = new DocumentSourceSearcher();
        DocumentSourceSearcher docSource2 = new DocumentSourceSearcher();

        Query q = new Query("/search?query=test");

        Result r1 = new Result(q);
        Result r2 = new Result(q);

        RootGroup root1 = new RootGroup(0, null);
        Group subGroup11 = new Group(new StringBucketId("a", "b"), new Relevance(1.0));
        subGroup11.add(new Group(new StringId("unique1"), new Relevance(1.0)));
        subGroup11.add(new Group(new StringId("unique5"), new Relevance(1.0)));
        subGroup11.add(new Group(new StringId("unique6"), new Relevance(1.0)));
        subGroup11.add(new Group(new StringId("unique7"), new Relevance(1.0)));
        root1.add(subGroup11);
        r1.hits().add(root1);
        docSource1.addResult(q, r1);

        RootGroup root2 = new RootGroup(0, null);
        Group subGroup21 = new Group(new StringBucketId("a", "b"), new Relevance(1.0));
        subGroup21.add(new Group(new StringId("unique1"), new Relevance(1.0)));
        subGroup21.add(new Group(new StringId("unique2"), new Relevance(1.0)));
        subGroup21.add(new Group(new StringId("unique3"), new Relevance(1.0)));
        root2.add(subGroup21);
        Group subGroup22 = new Group(new StringBucketId("c", "d"), new Relevance(1.0));
        subGroup22.add(new Group(new StringId("unique3"), new Relevance(1.0)));
        subGroup22.add(new Group(new StringId("unique4"), new Relevance(1.0)));
        root2.add(subGroup22);
        r2.hits().add(root2);
        docSource2.addResult(q, r2);

        BlendingSearcherWrapper blender = new BlendingSearcherWrapper();
        blender.addSource(new Chain<>("a", new FillSearcher(), docSource1));
        blender.addSource(new Chain<>("b", new FillSearcher(), docSource2));
        blender.initialize();
        q.setWindow(0, 10);
        Result result = new Execution(blender, Execution.Context.createContextStub()).search(q);
        assertEquals(2, result.hits().size());

        assertTrue(result.hits().get(0) instanceof RootGroup);
        RootGroup resultRoot1 = (RootGroup) result.hits().get(0);
        assertEquals(1, resultRoot1.asList().size());

        assertTrue(result.hits().get(1) instanceof RootGroup);
        RootGroup resultRoot2 = (RootGroup) result.hits().get(1);
        assertEquals(2, resultRoot2.asList().size());
    }
Disabled because the document source searcher does not handle being asked for
document sumaries for hits it did not create (it will insert the wrong values).
But are we sure fsearch handles this case correctly?
container-search/src/test/java/com/yahoo/prelude/searcher/test/BlendingSearcherTestCase.java