@Test
    void testTopLevelHitGroupFieldPropagation() {
        addChained(new MockSearcher(), "mySource1");
        addChained(new AnotherMockSearcher(), "mySource2");
        Chain<Searcher> mainChain = new Chain<>("default", createFederationSearcher());

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

        Result result = new Execution(mainChain, Execution.Context.createContextStub(chainRegistry)).search(q);
        assertNull(result.hits().getError());
        assertEquals("source:mySource1", result.hits().get(0).getId().stringValue());
        assertEquals("source:mySource2", result.hits().get(1).getId().stringValue());
        assertEquals(
                AnotherMockSearcher.IS_THIS_PROPAGATED,
                result.hits().get(1).getField(AnotherMockSearcher.PROPAGATION_KEY));
    }
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