Construct sample SearchResponse object with aggreagtion result for testing

I want to create a searchResponse object with aggregation results for testing.

I have tried the following

SearchResponseSections section = new SearchResponseSections(null, null, .......);

The first parameter here is for hits which I don't want but the second parameter which accepts Aggregations.

Now I am not able to create custom Aggregations object with buckets.

Code to test is as follows:

public AutoCompleteResponseDto getAutoCompleteResponse(SearchResponse searchResponse, String field, int limit) {
  Terms aggregation = searchResponse.getAggregations().get("typeAhead");
  final Set<String> bucketKeys = aggregation.getBuckets().stream().map(Terms.Bucket::getKeyAsString).collect(Collectors.toSet());
  return AutoCompleteResponseDto.builder().totalCount(bucketKeys.size()).values(bucketKeys).field(field).build();
}

I have also tried creating SearchResponse using Json as follows:

public static List<NamedXContentRegistry.Entry> getDefaultNamedXContents() {
  Map<String, ContextParser<Object, ? extends Aggregation>> map = new HashMap<>();
  map.put(StringTerms.NAME, (p, c) -> ParsedStringTerms.fromXContent(p, (String) c));
  return map.entrySet().stream().map(entry -> new NamedXContentRegistry.Entry(Aggregation.class, new ParseField(entry.getKey(), entry.getValue()))).collect(Collectors.toList());
}

public static SearchResponse getSearchResponse(String jsonString) {
  try {
    NamedXContentRegistry registry = new NamedXContentRegistry(getDefaultNamedXContents());
    XContentParser parser = new JsonXContentParser(registry, new JsonFactory().createParser(jsonString));
    return SearchResponse.fromXContent(parser);
  } catch (Exception ex) {
  }
  return new SearchResponse(); 
}

I am calling the getSearchResponse(json) method with the following Json:

{
  "took": 65,
  "timed_out": false,
  "_shards": {
    "total": 5,
    "successful": 5,
    "skipped": 0,
    "failed": 0
  },
  "aggregations": {
    "typeAhead": {
      "buckets": [
        {
          "key": "1002312321",
          "docCount": 31521
        }
      ]
    }
  }
}

And getting the ParseException: [could not parse the aggregation keyed as [typeAhead]].

ElasticSearch version = 5.6.15

PS: Please ignore typo if any.