FreeCheckers.hpp

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//                Copyright Oliver J. Rosten 2020.                //
// Distributed under the GNU GENERAL PUBLIC LICENSE, Version 3.0. //
//    (See accompanying file LICENSE.md or copy at                //
//          https://www.gnu.org/licenses/gpl-3.0.en.html)         //
 
#pragma once
 
#include "sequoia/TestFramework/CoreInfrastructure.hpp"
#include "sequoia/TestFramework/BinaryRelationships.hpp"
#include "sequoia/TestFramework/Advice.hpp"
#include "sequoia/TestFramework/TestLogger.hpp"
#include "sequoia/Core/Meta/Utilities.hpp"
 
#include <format>
 
namespace sequoia::testing
{
 
  template<class T> struct value_tester;
 
  //=========================== Types used to generate overload sets ===========================//
 
  struct equality_check_t {};
  struct simple_equality_check_t {};
 
  template<class ValueBasedCustomizer>
  struct general_equivalence_check_t
  {
    using customizer_type = ValueBasedCustomizer;
 
    template<class Customizer>
    using rebind_check_type = general_equivalence_check_t<Customizer>;
 
    customizer_type customizer;
  };
 
  template<class ValueBasedCustomizer>
    requires std::is_void_v<ValueBasedCustomizer>
  struct general_equivalence_check_t<ValueBasedCustomizer>
  {
    using fallback = equality_check_t;
  };
 
  using equivalence_check_t = general_equivalence_check_t<void>;
 
  template<class ValueBasedCustomizer>
  struct general_weak_equivalence_check_t
  {
    using customizer_type = ValueBasedCustomizer;
 
    template<class Customizer>
    using rebind_check_type = general_weak_equivalence_check_t<Customizer>;
 
    customizer_type customizer;
  };
 
  template<class ValueBasedCustomizer>
    requires std::is_void_v<ValueBasedCustomizer>
  struct general_weak_equivalence_check_t<ValueBasedCustomizer>
  {
    using fallback = general_equivalence_check_t<ValueBasedCustomizer>;
  };
 
  using weak_equivalence_check_t = general_weak_equivalence_check_t<void>;
 
  enum class minimal_reporting_permitted : bool { no, yes };
 
  template<minimal_reporting_permitted MinimalReporting>
  struct with_best_available_check_t {};
 
  template<class ValueBasedCustomizer>
  [[nodiscard]]
  std::string to_string(general_equivalence_check_t<ValueBasedCustomizer>)
  {
    return "equivalence";
  }
 
  template<class ValueBasedCustomizer>
  [[nodiscard]]
  std::string to_string(general_weak_equivalence_check_t<ValueBasedCustomizer>)
  {
    return "weak equivalence";
  }
 
  //=========================== Values defined for convenience ===========================//
 
  inline constexpr equality_check_t            equality{};  
  inline constexpr simple_equality_check_t     simple_equality{};
  inline constexpr equivalence_check_t         equivalence{};
  inline constexpr weak_equivalence_check_t    weak_equivalence{};
  inline constexpr with_best_available_check_t<minimal_reporting_permitted::no> with_best_available{};
 
  template<class T>
  inline constexpr bool is_elementary_check{
       std::is_same_v<T, equality_check_t>
    || std::is_same_v<T, simple_equality_check_t>
    || std::is_same_v<T, equivalence_check_t>
    || std::is_same_v<T, weak_equivalence_check_t>
  };
 
  template<class T>
  inline constexpr bool is_best_available_check{
       std::is_same_v<T, with_best_available_check_t<minimal_reporting_permitted::yes>>
    || std::is_same_v<T, with_best_available_check_t<minimal_reporting_permitted::no>>
  };
  
  template<class T>
  inline constexpr bool is_customized_check{
    requires {
      typename T::customizer_type;
      typename T::template rebind_check_type<typename T::customizer_type>;
      requires std::is_same_v<typename T::template rebind_check_type<typename T::customizer_type>, T>;
    }
  };
 
  template<class T>
  inline constexpr bool is_general_equivalence_check{is_customized_check<T> || std::is_same_v<T, equivalence_check_t> || std::is_same_v<T, weak_equivalence_check_t>};
 
  template<class Compare, class T>
  inline constexpr bool potential_comparator_for{
       std::is_invocable_r_v<bool, Compare, T, T>
    || (faithful_range<T> && !(is_elementary_check<Compare> || is_best_available_check<Compare> || is_customized_check<Compare>))
  };
 
  template<class CheckType, test_mode Mode, class T, class U, class... Args>
  concept tests_against = requires(CheckType c, test_logger<Mode>& logger, T&& obtained, const U& predicted, Args&&... args) {
    value_tester<std::remove_cvref_t<T>>::test(c, logger, std::forward<T>(obtained), predicted, std::forward<Args>(args)...);
  };
 
  template<class CheckType, test_mode Mode, class T, class U, class Tutor>
  concept tests_against_with_or_without_tutor = tests_against<CheckType, Mode, T, U, Tutor> || tests_against<CheckType, Mode, T, U>;
 
  template<class CheckType, test_mode Mode, class T, class U, class Tutor>
  concept checkable_against = requires(CheckType c, test_logger<Mode>& logger, T&& obtained, const U& predicted, Tutor tutor) {
    check(c, "", logger, std::forward<T>(obtained), predicted, tutor);
  };
 
  template<class CheckType, test_mode Mode, class T, class U, class Tutor>
  inline constexpr bool checkable_against_fallback{
    requires {
      typename CheckType::fallback;
      requires checkable_against<typename CheckType::fallback, Mode, T, U, Tutor>;
    }
  };
 
  template<test_mode Mode, class T, class U, class Tutor>
  inline constexpr bool has_elementary_check_against{
       checkable_against<equality_check_t,         Mode, T, U, Tutor>
    || checkable_against<simple_equality_check_t,  Mode, T, U, Tutor>
    || checkable_against<equivalence_check_t,      Mode, T, U, Tutor>
    || checkable_against<weak_equivalence_check_t, Mode, T, U, Tutor>
  };
 
  template<class>
  struct exception_message_extractor;
 
  template<class E>
  requires std::derived_from<E, std::exception>
    struct exception_message_extractor<E>
  {
    [[nodiscard]]
    static std::string get(const E& e) { return e.what(); }
  };
 
  template<class E>
    requires (!std::derived_from<E, std::exception>) && serializable<E>
  struct exception_message_extractor<E>
  {
    [[nodiscard]]
    static std::string get(const E& e) { return to_string(e); }
  };
 
  template<class CheckType, test_mode Mode, class T, class U, class Advisor>
    requires tests_against_with_or_without_tutor<CheckType, Mode, T, U, tutor<Advisor>>
  void select_test(CheckType flavour, test_logger<Mode>& logger, const T& obtained, const U& prediction, [[maybe_unused]] tutor<Advisor> advisor)
  {
    if constexpr(tests_against<CheckType, Mode, T, U, tutor<Advisor>>)
    {
      value_tester<T>::test(flavour, logger, obtained, prediction, advisor);
    }
    else if constexpr(tests_against<CheckType, Mode, T, U>)
    {
      value_tester<T>::test(flavour, logger, obtained, prediction);
    }
    else
    {
      static_assert(dependent_false<CheckType>::value, "Should never be triggered; indicates mismatch between requirement and logic");
    }
  }
 
  template<class CheckType, test_mode Mode, class T, class U, class Advisor>
    requires is_general_equivalence_check<CheckType> && tests_against_with_or_without_tutor<CheckType, Mode, T, U, tutor<Advisor>>
  bool general_equivalence_check(CheckType flavour,
                                 std::string description,
                                 test_logger<Mode>& logger,
                                 const T& obtained,
                                 const U& predicted,
                                 tutor<Advisor> advisor)
  {
    const auto msg{
      [] (CheckType flavour, std::string desc) -> std::string {
          return append_lines(desc,
                              "Comparison performed using:",
                              make_type_info<value_tester<T>>(),
                              std::format("Checking for {} with:", to_string(flavour)), make_type_info<U>()).append("\n");
      }
    };
 
    sentinel<Mode> sentry{logger, msg(flavour, std::move(description))};
 
    select_test(flavour, logger, obtained, predicted, advisor);
 
    return !sentry.failure_detected();
  }
 
  template<bool IsFinalMessage, test_mode Mode, class Compare, class T, class Advisor>
    requires std::is_invocable_r_v<bool, Compare, T, T> && (!IsFinalMessage || reportable<T>)
  void binary_comparison(final_message_constant<IsFinalMessage>, sentinel<Mode>& sentry, Compare compare, const T& obtained, const T& prediction, tutor<Advisor> advisor)
  {
    sentry.log_check();
    if(!compare(obtained, prediction))
    {
      std::string message{failure_reporter<Compare>::reporter(final_message_constant<IsFinalMessage>{}, compare, obtained, prediction)};
      append_advice(message, {advisor, obtained, prediction});
 
      sentry.log_failure(message);
    }
  }
 
  struct default_exception_message_postprocessor
  {
    [[nodiscard]]
    std::string operator()(const project_paths& projPaths, std::string message) const
    {
      constexpr auto npos{std::string::npos};
      if(const auto pos{message.find(projPaths.project_root().generic_string())}; pos < npos)
      {
        const auto len{projPaths.project_root().generic_string().size()};
        message.erase(pos, len + 1);
      }
      
      return message;
    }
  };
 
  //================= namespace-level check functions =================//
  
  template
  <
    class E,
    test_mode Mode,
    class Fn,
    invocable_r<std::string, project_paths, std::string> Postprocessor=default_exception_message_postprocessor
  >
  bool check_exception_thrown(std::string description, test_logger<Mode>& logger, Fn&& function, const project_paths& projPaths, Postprocessor postprocessor={})
  {
    auto message{
      [&description]() -> std::string&& {
        return std::move(append_lines(description, "Expected Exception Type:", make_type_info<E>()));
      }()
    };
 
    sentinel<Mode> sentry{logger, message};
    sentry.log_check();
    try
    {
      std::forward<Fn>(function)();
      sentry.log_failure("No exception thrown");
      return false;
    }
    catch(const E& e)
    {
      sentry.log_caught_exception_message(postprocessor(projPaths, exception_message_extractor<E>::get(e)));
      return true;
    }
    catch(const std::exception& e)
    {
      std::string msg{append_lines("Unexpected exception thrown (caught by std::exception&):", "\"").append(e.what()).append("\"\n")};
 
      sentry.log_failure(msg);
      return false;
    }
    catch(...)
    {
      sentry.log_failure("Unknown exception thrown\n");
      return false;
    }
  }
 
  template<class CheckType, test_mode Mode, std::input_or_output_iterator Iter, std::input_or_output_iterator PredictionIter, class Advisor>
  inline constexpr bool supports_iterator_range_check{checkable_against<CheckType, Mode, std::iter_value_t<Iter>, std::iter_value_t<PredictionIter>, tutor<Advisor>>};
  
  template
  <
    class CheckType,
    test_mode Mode,
    std::input_or_output_iterator Iter,
    std::sentinel_for<Iter> Sentinel,
    std::input_or_output_iterator PredictionIter,
    std::sentinel_for<PredictionIter> PredictionSentinel,
    class Advisor = null_advisor
  >
    requires supports_iterator_range_check<CheckType, Mode, Iter, PredictionIter, Advisor>
  bool check(CheckType flavour,
             std::string description,
             test_logger<Mode>& logger,
             Iter first,
             Sentinel last,
             PredictionIter predictionFirst,
             PredictionSentinel predictionLast,
             tutor<Advisor> advisor = {})
  {
    auto info{
      [&description]() -> std::string&& {
        return description.empty() || description.back() == '\n' ? std::move(description) : std::move(description.append("\n"));
      }
    };
 
    sentinel<Mode> sentry{logger, info()};
    bool equal{true};
 
    const auto actualSize{fixed_width_unsigned_cast(std::ranges::distance(first, last))};
    const auto predictedSize{fixed_width_unsigned_cast(std::ranges::distance(predictionFirst, predictionLast))};
    if(check(equality, "Container size wrong", logger, actualSize, predictedSize))
    {      
      auto predictionIter{predictionFirst};
      auto iter{first};
      for(; predictionIter != predictionLast; std::ranges::advance(predictionIter, 1), std::ranges::advance(iter, 1))
      {
        const auto dist{std::ranges::distance(predictionFirst, predictionIter)};
        auto mess{std::format("Element {} of range incorrect", dist)};
        if(!check(flavour, std::move(mess), logger, *iter, *predictionIter, advisor)) equal = false;
      }
    }
    else
    {
      equal = false;
    }
 
    return equal;
  }
 
  template<class Compare, test_mode Mode, class T, class Advisor=null_advisor>
    requires potential_comparator_for<Compare, T>
  bool check(Compare compare,
             std::string description,
             test_logger<Mode>& logger,
             const T& obtained,
             const T& prediction,
             tutor<Advisor> advisor={})
  {
    sentinel<Mode> sentry{logger, add_type_info<T>(std::move(description))};
 
    if constexpr(std::is_invocable_r_v<bool, Compare, T, T>)
    {
      using finality = final_message_constant<!faithful_range<T>>;
      binary_comparison(finality{}, sentry, std::move(compare), obtained, prediction, advisor);
    }
    else
    {
      check(std::move(compare), "", logger, obtained.begin(), obtained.end(), prediction.begin(), prediction.end(), advisor);
    }
 
    return !sentry.failure_detected();
  }
 
  namespace impl
  {
    template<class CheckType, test_mode Mode, faithful_range T, faithful_range U, class Advisor>
    inline constexpr bool supports_range_check_v{
      requires(T& t, U& u) {
         requires supports_iterator_range_check<CheckType, Mode, decltype(std::ranges::begin(t)), decltype(std::ranges::begin(u)), Advisor>;
       }
    };
  }
 
  template<class CheckType, test_mode Mode, class T, class U, class Advisor>
  struct supports_range_check : std::false_type {};
 
  template<class CheckType, test_mode Mode, faithful_range T, faithful_range U, class Advisor>
  requires impl::supports_range_check_v<CheckType, Mode, T, U, Advisor>
  struct supports_range_check<CheckType, Mode, T, U, Advisor> : std::true_type {};
 
  template<class CheckType, test_mode Mode, class T, class U, class Advisor>
  inline constexpr bool supports_range_check_v{supports_range_check<CheckType, Mode, T, U, Advisor>::value};
  
  template<test_mode Mode, class T, class Advisor>
  inline constexpr bool supports_equality_check{
       (deep_equality_comparable<T> && reportable<T>)
    || tests_against_with_or_without_tutor<equality_check_t, Mode, T, T, tutor<Advisor>>
    || supports_range_check_v<equality_check_t, Mode, T, T, Advisor>
  };
 
  template<test_mode Mode, class T, class Advisor=null_advisor>
    requires supports_equality_check<Mode, T, Advisor>
  bool check(equality_check_t,
             std::string description,
             test_logger<Mode>& logger,
             const T& obtained,
             const T& prediction,
             tutor<Advisor> advisor={})
  {
    sentinel<Mode> sentry{logger, add_type_info<T>(std::move(description))};
 
    if constexpr(deep_equality_comparable<T>)
    {
      using finality = final_message_constant<!(tests_against_with_or_without_tutor<equality_check_t, Mode, T, T, tutor<Advisor>> || faithful_range<T>)>;
      binary_comparison(finality{}, sentry, std::ranges::equal_to{}, obtained, prediction, advisor);
    }
 
    if constexpr(tests_against_with_or_without_tutor<equality_check_t, Mode, T, T, tutor<Advisor>>)
    {
      select_test(equality_check_t{}, logger, obtained, prediction, advisor);
    }
    else if constexpr(supports_range_check_v<equality_check_t, Mode, T, T, Advisor>)
    {
      check(equality, "", logger, std::begin(obtained), std::end(obtained), std::begin(prediction), std::end(prediction), advisor);
    }
 
    return !sentry.failure_detected();
  }
 
  template<test_mode Mode, class T, class Advisor>
  inline constexpr bool supports_simple_equality_check{
       (deep_equality_comparable<T> && reportable<T>)
    || supports_range_check_v<simple_equality_check_t, Mode, T, T, Advisor>
  };
 
  template<test_mode Mode, class T, class Advisor=null_advisor>
    requires supports_simple_equality_check<Mode, T, Advisor>
  bool check(simple_equality_check_t,
             std::string description,
             test_logger<Mode>& logger,
             const T& obtained,
             const T& prediction,
             tutor<Advisor> advisor={})
  {
    sentinel<Mode> sentry{logger, add_type_info<T>(std::move(description))};
 
    using finality = final_message_constant<!faithful_range<T>>;
    binary_comparison(finality{}, sentry, std::ranges::equal_to{}, obtained, prediction, advisor);
 
    if constexpr(supports_range_check_v<simple_equality_check_t, Mode, T, T, Advisor>)
    {
      check(simple_equality, "", logger, std::begin(obtained), std::end(obtained), std::begin(prediction), std::end(prediction), advisor);
    }
 
    return !sentry.failure_detected();
  }
 
  template<class CheckType, test_mode Mode, class T, class U, class Advisor>
  inline constexpr bool supports_generalized_equivalence_check{
       is_general_equivalence_check<CheckType>
    && (   tests_against_with_or_without_tutor<CheckType, Mode, T, U, tutor<Advisor>>
        || supports_range_check_v<CheckType, Mode, T, U, Advisor>
        || checkable_against_fallback<CheckType, Mode, T, U, tutor<Advisor>>)
  };
  
  template<class CheckType, test_mode Mode, class T, class U, class Advisor=null_advisor>
    requires supports_generalized_equivalence_check<CheckType, Mode, T, U, Advisor>
  bool check(CheckType flavour, std::string description, test_logger<Mode>& logger, const T& obtained, const U& prediction, tutor<Advisor> advisor={})
  {
    if constexpr(tests_against_with_or_without_tutor<CheckType, Mode, T, U, tutor<Advisor>>)
    {
      return general_equivalence_check(flavour,
                                       std::move(description),
                                       logger,
                                       obtained,
                                       prediction,
                                       advisor);
    }
    else if constexpr(supports_range_check_v<CheckType, Mode, T, U, Advisor>)
    {
      return check(flavour,
                   add_type_info<T>(std::move(description)),
                   logger,
                   std::begin(obtained),
                   std::end(obtained),
                   std::begin(prediction),
                   std::end(prediction),
                   advisor);
    }
    else if constexpr(checkable_against_fallback<CheckType, Mode, T, U, tutor<Advisor>>)
    {
      using fallback = typename CheckType::fallback;
      return check(fallback{},
                   std::move(description),
                   logger,
                   obtained,
                   prediction,
                   advisor);
    }
    else
    {
      static_assert(dependent_false<CheckType>::value, "Should never be triggered; indicates mismatch between requirement and logic");
    }
  }  
 
  template<minimal_reporting_permitted MinimalReporting, test_mode Mode, class T, class U, class Advisor>
  inline constexpr bool supports_best_available_check{
       tests_against_with_or_without_tutor<with_best_available_check_t<MinimalReporting>, Mode, T, U, tutor<Advisor>>
    || has_elementary_check_against<Mode, T, U, tutor<Advisor>>
    || supports_range_check_v<with_best_available_check_t<MinimalReporting>, Mode, T, U, Advisor>
    || (std::is_same_v<T, U> && deep_equality_comparable<T> && reportable<T>)
    || ((MinimalReporting == minimal_reporting_permitted::yes) && std::equality_comparable_with<T, U>)
  };
  
  template<minimal_reporting_permitted MinimalReporting, test_mode Mode, class T, class U, class Advisor=null_advisor>
    requires supports_best_available_check<MinimalReporting, Mode, T, U, Advisor>
  bool check(with_best_available_check_t<MinimalReporting>,
             std::string description,
             test_logger<Mode>& logger,
             const T& obtained,
             const U& prediction,
             tutor<Advisor> advisor={})
  {
    if constexpr(tests_against_with_or_without_tutor<with_best_available_check_t<MinimalReporting>, Mode, T, U, tutor<Advisor>>)
    {
      sentinel<Mode> sentry{logger, add_type_info<T>(std::move(description))};
 
      if constexpr(std::is_same_v<T, U> && deep_equality_comparable<T>)
      {
        binary_comparison(is_not_final_message_t{}, sentry, std::ranges::equal_to{}, obtained, prediction, advisor);
      }
 
      select_test(with_best_available, logger, obtained, prediction, advisor);
 
      return !sentry.failure_detected();
    }
    else if constexpr(std::is_same_v<T, U> && tests_against_with_or_without_tutor<equality_check_t, Mode, T, U, tutor<Advisor>>)
    {
      return check(equality, description, logger, obtained, prediction, advisor);
    }
    else if constexpr(tests_against_with_or_without_tutor<equivalence_check_t, Mode, T, U, tutor<Advisor>>)
    {
      return check(equivalence, description, logger, obtained, prediction, advisor);
    }
    else if constexpr(tests_against_with_or_without_tutor<weak_equivalence_check_t, Mode, T, U, tutor<Advisor>>)
    {
      return check(weak_equivalence, description, logger, obtained, prediction, advisor);
    }
    else if constexpr(supports_range_check_v<with_best_available_check_t<MinimalReporting>, Mode, T, U, Advisor>)
    {
      return check(with_best_available, description, logger, std::begin(obtained), std::end(obtained), std::begin(prediction), std::end(prediction), advisor);
    } 
    else if constexpr(std::is_same_v<T, U> && deep_equality_comparable<T> && reportable<T>)
    {
      return check(simple_equality, description, logger, obtained, prediction, advisor);
    }
    else if constexpr((MinimalReporting == minimal_reporting_permitted::yes) && std::equality_comparable_with<T, U>)
    {
      return check(description, logger, obtained == prediction,advisor);
    }
    else
    {
      static_assert(false);
    }
  }
 
  template<test_mode Mode, class Advisor=null_advisor>
  bool check(std::string description, test_logger<Mode>& logger, const bool obtained, tutor<Advisor> advisor={})
  {
    return check(equality, std::move(description), logger, obtained, true, std::move(advisor));
  }
 
  template<test_mode Mode, class Extender>
  class checker : public Extender
  {
    friend Extender;
  public:
    constexpr static test_mode mode{Mode};
    using logger_type = test_logger<Mode>;
 
    checker() = default;
 
    checker(const checker&)            = delete;
    checker& operator=(const checker&) = delete;
 
    template<class T, class Advisor = null_advisor, class Self>
      requires supports_equality_check<Mode, T, Advisor>
    bool check(this Self& self, equality_check_t, const reporter& description, const T& obtained, const T& prediction, tutor<Advisor> advisor = {})
    {
      return testing::check(equality, self.report(description), self.m_Logger, obtained, prediction, std::move(advisor));
    }
 
    template<class T, class Advisor = null_advisor, class Self>
      requires supports_simple_equality_check<Mode, T, Advisor>
    bool check(this Self& self, simple_equality_check_t, const reporter& description, const T& obtained, const T& prediction, tutor<Advisor> advisor = {})
    {
        return testing::check(simple_equality, self.report(description), self.m_Logger, obtained, prediction, std::move(advisor));
    }
 
    template<class T, class U, minimal_reporting_permitted MinimalReporting, class Advisor = null_advisor, class Self>
      requires supports_best_available_check<MinimalReporting, Mode, T, U, Advisor>
    bool check(this Self& self, with_best_available_check_t<MinimalReporting>, const reporter& description, const T& obtained, const U& prediction, tutor<Advisor> advisor = {})
    {
      return testing::check(with_best_available_check_t<MinimalReporting>{},
                            self.report(description),
                            self.m_Logger,
                            obtained,
                            prediction,
                            std::move(advisor));
    }
 
    template<class ValueBasedCustomizer, class T, class U, class Advisor = null_advisor, class Self>
      requires supports_generalized_equivalence_check<general_equivalence_check_t<ValueBasedCustomizer>, Mode, T, U, Advisor>
    bool check(this Self& self, general_equivalence_check_t<ValueBasedCustomizer> checker, const reporter& description, const T& obtained, const U& prediction, tutor<Advisor> advisor = {})
    {
      return testing::check(checker, self.report(description), self.m_Logger, obtained, prediction, std::move(advisor));
    }
 
    template<class ValueBasedCustomizer, class T, class U, class Advisor = null_advisor, class Self>
      requires supports_generalized_equivalence_check<general_weak_equivalence_check_t<ValueBasedCustomizer>, Mode, T, U, Advisor>
    bool check(this Self& self, general_weak_equivalence_check_t<ValueBasedCustomizer> checker, const reporter& description, const T& obtained, const U& prediction, tutor<Advisor> advisor = {})
    {
      return testing::check(checker, self.report(description), self.m_Logger, obtained, prediction, std::move(advisor));
    }
 
    template<class Compare, class T, class Advisor = null_advisor, class Self>
      requires potential_comparator_for<Compare, T>
    bool check(this Self& self, Compare compare, const reporter& description, const T& obtained, const T& prediction, tutor<Advisor> advisor = {})
    {
      return testing::check(std::move(compare), self.report(description), self.m_Logger, obtained, prediction, std::move(advisor));
    }
 
    template<class Advisor=null_advisor, class Self>
    bool check(this Self& self, const reporter& description, const bool obtained, tutor<Advisor> advisor={})
    {
      return testing::check(self.report(description), self.m_Logger, obtained, std::move(advisor));
    }
 
    template
    <
      class Compare,
      std::input_or_output_iterator Iter,
      std::sentinel_for<Iter> Sentinel,
      std::input_or_output_iterator PredictionIter,
      std::sentinel_for<PredictionIter> PredictionSentinel,
      class Advisor = null_advisor,
      class Self
    >
      requires supports_iterator_range_check<Compare, Mode, Iter, PredictionIter, Advisor>
    bool check(this Self& self,
               Compare compare,
               const reporter& description,
               Iter first,
               Sentinel last,
               PredictionIter predictionFirst,
               PredictionSentinel predictionLast,
               tutor<Advisor> advisor={})
    {
      return testing::check(std::move(compare), self.report(description), self.m_Logger, first, last, predictionFirst, predictionLast, std::move(advisor));
    }
 
    template
    <
      class E,
      class Fn,
      invocable_r<std::string, project_paths, std::string> Postprocessor=default_exception_message_postprocessor,
      class Self
    >
    bool check_exception_thrown(this Self& self, const reporter& description, Fn&& function, Postprocessor postprocessor={})
    {
      return testing::check_exception_thrown<E>(self.report(description), self.m_Logger, std::forward<Fn>(function), self.get_project_paths(), std::move(postprocessor));
    }
    
#define STATIC_CHECK(...) (check("", [](){ static_assert(__VA_ARGS__); return true; }()))
 
    template<class Stream>
      requires serializable_to<Stream, test_logger<Mode>>
    friend Stream& operator<<(Stream& os, const checker& c)
    {
      os << c.m_Logger;
      return os;
    }
 
    [[nodiscard]]
    log_summary summary(std::string_view prefix, const log_summary::duration delta) const
    {
      return log_summary{prefix, m_Logger, delta};
    }
 
    void reset_results() noexcept { m_Logger.reset_results(); }
 
    [[nodiscard]]
    bool has_critical_failures() const noexcept
    {
      return m_Logger.results().critical_failures > 0;
    }
  protected:
    explicit checker(active_recovery_files recovery)
      : m_Logger{std::move(recovery)}
    {}
 
    checker(checker&&)            noexcept = default;
    checker& operator=(checker&&) noexcept = default;
 
    ~checker() = default;
 
    [[nodiscard]]
    std::size_t checks() const noexcept { return m_Logger.checks(); }
 
    [[nodiscard]]
    std::size_t failures() const noexcept { return m_Logger.failures(); }
 
    [[nodiscard]]
    const uncaught_exception_info& exceptions_detected_by_sentinel() const noexcept
    {
      return m_Logger.exceptions_detected_by_sentinel();
    }
 
    [[nodiscard]]
    sentinel<Mode> make_sentinel(std::string message)
    {
      return {m_Logger, std::move(message)};
    }
 
    [[nodiscard]]
    std::string_view top_level_message() const
    {
      return m_Logger.top_level_message();
    }
 
    [[nodiscard]]
    const failure_output& failure_messages() const noexcept
    {
      return m_Logger.results().failure_messages;
    }
  private:
    test_logger<Mode> m_Logger;
  };
}