Fixed failed test after knn pushed multiple inner hits feature (#1026) (

#1027)

Signed-off-by: Martin Gaievski <gaievski@amazon.com>
(cherry picked from commit 3d72cc3)

Co-authored-by: Martin Gaievski <gaievski@amazon.com>

src/test/java/org/opensearch/neuralsearch/query/HybridQueryBuilderTests.java

@@ -67,6 +67,7 @@
 import org.opensearch.knn.index.mapper.KNNVectorFieldType;
 import org.opensearch.knn.index.query.KNNQuery;
 import org.opensearch.knn.index.query.KNNQueryBuilder;
+import org.opensearch.knn.index.query.nativelib.NativeEngineKnnVectorQuery;
 import org.opensearch.neuralsearch.util.NeuralSearchClusterTestUtils;
 import org.opensearch.neuralsearch.util.NeuralSearchClusterUtil;
 
@@ -141,8 +142,8 @@ public void testDoToQuery_whenOneSubquery_thenBuildSuccessfully() {
         assertNotNull(queryOnlyNeural);
         assertTrue(queryOnlyNeural instanceof HybridQuery);
         assertEquals(1, ((HybridQuery) queryOnlyNeural).getSubQueries().size());
-        assertTrue(((HybridQuery) queryOnlyNeural).getSubQueries().iterator().next() instanceof KNNQuery);
-        KNNQuery knnQuery = (KNNQuery) ((HybridQuery) queryOnlyNeural).getSubQueries().iterator().next();
+        assertTrue(((HybridQuery) queryOnlyNeural).getSubQueries().iterator().next() instanceof NativeEngineKnnVectorQuery);
+        KNNQuery knnQuery = ((NativeEngineKnnVectorQuery) ((HybridQuery) queryOnlyNeural).getSubQueries().iterator().next()).getKnnQuery();
         assertEquals(VECTOR_FIELD_NAME, knnQuery.getField());
         assertEquals(K, knnQuery.getK());
         assertNotNull(knnQuery.getQueryVector());
@@ -183,8 +184,8 @@ public void testDoToQuery_whenMultipleSubqueries_thenBuildSuccessfully() {
         // verify knn vector query
         Iterator<Query> queryIterator = ((HybridQuery) queryTwoSubQueries).getSubQueries().iterator();
         Query firstQuery = queryIterator.next();
-        assertTrue(firstQuery instanceof KNNQuery);
-        KNNQuery knnQuery = (KNNQuery) firstQuery;
+        assertTrue(firstQuery instanceof NativeEngineKnnVectorQuery);
+        KNNQuery knnQuery = ((NativeEngineKnnVectorQuery) firstQuery).getKnnQuery();
         assertEquals(VECTOR_FIELD_NAME, knnQuery.getField());
         assertEquals(K, knnQuery.getK());
         assertNotNull(knnQuery.getQueryVector());