_test(request, source = null, id = null) {
    return koncordeTest(
      global.kuzzle.koncorde,
      request.input.args.index,
      request.input.args.collection,
      source || request.input.body || {},
      id || request.input.args._id,
    );
  }
DRYification for calls to Koncorde's test method from a Request object
@param {Request} request
@param {Object} source - document's source
@param {String} id

@returns {Array.<string>}