text: ////////////////////////////////////////////////////////////////////////////////
  /// DISCLAIMER
  ///
  /// Copyright 2019 ArangoDB GmbH, Cologne, Germany
  ///
  /// Licensed under the Apache License, Version 2.0 (the "License");
  /// you may not use this file except in compliance with the License.
  /// You may obtain a copy of the License at
  ///
  ///     http://www.apache.org/licenses/LICENSE-2.0
  ///
  /// Unless required by applicable law or agreed to in writing, software
  /// distributed under the License is distributed on an "AS IS" BASIS,
  /// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  /// See the License for the specific language governing permissions and
  /// limitations under the License.
  ///
  /// Copyright holder is ArangoDB GmbH, Cologne, Germany
  ///
  /// @author Tobias Gödderz
  ////////////////////////////////////////////////////////////////////////////////
  
  #ifndef TESTS_AQL_MULTIDEPFETCHERHELPER_H
  #define TESTS_AQL_MULTIDEPFETCHERHELPER_H
  
  #include "Aql/ExecutionBlock.h"
  #include "Aql/ExecutionState.h"
  #include "Aql/ExecutionStats.h"
  #include "Aql/MultiDependencySingleRowFetcher.h"
  #include "Aql/OutputAqlItemRow.h"
  #include "Aql/SharedAqlItemBlockPtr.h"
  
  #include <boost/variant.hpp>
  
  #include <tuple>
  
  namespace arangodb {
  namespace tests {
  namespace aql {
  
  // std::pair<ExecutionState, size_t> preFetchNumberOfRows(size_t atMost)
  struct PrefetchNumberOfRows {
    using Result = std::pair<arangodb::aql::ExecutionState, size_t>;
    size_t atMost;
  };
  
  // std::pair<ExecutionState, InputAqlItemRow> fetchRowForDependency(size_t dependency, size_t atMost)
  struct FetchRowForDependency {
    using Result = std::pair<arangodb::aql::ExecutionState, arangodb::aql::InputAqlItemRow>;
    size_t dependency;
    size_t atMost;
  };
  
  // std::pair<ExecutionState, size_t> skipRowsForDependency(size_t dependency, size_t atMost);
  struct SkipRowsForDependency {
    using Result = std::pair<arangodb::aql::ExecutionState, size_t>;
    size_t dependency;
    size_t atMost;
  };
  
  // std::pair<ExecutionState, ShadowAqlItemRow> fetchShadowRow(size_t atMost);
  struct FetchShadowRow {
    using Result = std::pair<arangodb::aql::ExecutionState, arangodb::aql::ShadowAqlItemRow>;
    size_t atMost;
  };
  
  template <class FetcherCallT>
  using ConcreteFetcherIOPair = std::pair<FetcherCallT, typename FetcherCallT::Result>;
  
  using FetcherIOPair =
      boost::variant<ConcreteFetcherIOPair<PrefetchNumberOfRows>, ConcreteFetcherIOPair<FetchRowForDependency>,
                     ConcreteFetcherIOPair<SkipRowsForDependency>, ConcreteFetcherIOPair<FetchShadowRow>>;
  
  void runFetcher(arangodb::aql::MultiDependencySingleRowFetcher& testee,
                  std::vector<FetcherIOPair> const& inputOutputPairs);
  
  }  // namespace aql
  }  // namespace tests
  }  // namespace arangodb
  
  #endif  // TESTS_AQL_MULTIDEPFETCHERHELPER_H
  