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// Copyright (c) 2026 Progmasoft.
// SPDX-License-Identifier: MPL-2.0 WITH AdditionRef-Progmasoft-Exception-1.1
#pragma once
#include <catch2/catch_tostring.hpp>
#include <Progmasoft/Catch3/Generator.hpp>
#include <concepts>
#include <cstddef>
#include <cstdint>
#include <exception>
#include <functional>
#include <optional>
#include <sstream>
#include <string>
#include <type_traits>
#include <utility>
namespace Progmasoft::Catch3 {
/// Controls a property run without changing the compatibility runner's CLI.
struct PropertyOptions final {
std::size_t Trials = 100;
std::uint64_t Seed = 0xC47C4A53ULL;
std::size_t MaxShrinkSteps = 1000;
};
enum class PropertyStatus : std::uint8_t {
kPassed,
kFailed,
kErrored,
kInvalidConfiguration,
};
struct PropertyFailure final {
std::uint64_t RootSeed = 0;
std::uint64_t TrialSeed = 0;
std::size_t Trial = 0;
std::size_t ShrinkSteps = 0;
std::string Counterexample;
std::string Reason;
};
/// Stable, machine-readable outcome with a deterministic human-readable
/// report.
struct PropertyResult final {
PropertyStatus Status = PropertyStatus::kPassed;
std::size_t TrialsRun = 0;
std::optional<PropertyFailure> Failure;
std::string Error;
[[nodiscard]] bool Succeeded() const noexcept {
return Status == PropertyStatus::kPassed;
}
[[nodiscard]] std::string Describe() const {
std::ostringstream output;
switch ( Status ) {
case PropertyStatus::kPassed:
output << "property passed: " << TrialsRun << " trials";
return output.str();
case PropertyStatus::kInvalidConfiguration:
output << "invalid property configuration: " << Error;
return output.str();
case PropertyStatus::kErrored:
output << "property execution errored after " << TrialsRun
<< " trials: " << Error;
break;
case PropertyStatus::kFailed:
output << "property failed after " << TrialsRun << " trials";
break;
}
if ( Failure.has_value() ) {
output << "; failing trial " << Failure->Trial << ", root seed "
<< Failure->RootSeed << ", replay seed "
<< Failure->TrialSeed << ", shrink checks "
<< Failure->ShrinkSteps
<< "\ncounterexample: " << Failure->Counterexample
<< "\nreason: " << Failure->Reason;
}
return output.str();
}
};
namespace Detail {
template <typename ValueType>
[[nodiscard]] std::string
StringifyPropertyValue( const ValueType& value ) {
return Catch::StringMaker<std::remove_cvref_t<ValueType>>::convert(
value );
}
template <typename Predicate, typename ValueType>
[[nodiscard]] std::optional<std::string>
EvaluateProperty( Predicate& predicate, const ValueType& value ) {
try {
if ( static_cast<bool>( std::invoke( predicate, value ) ) ) {
return std::nullopt;
}
return "predicate returned false";
} catch ( const std::exception& exception ) {
return std::string( "predicate threw std::exception: " ) +
exception.what();
} catch ( ... ) {
return "predicate threw a non-standard exception";
}
}
template <typename ValueType>
[[nodiscard]] std::string
DescribeValue( const ValueType& value ) noexcept {
try {
return StringifyPropertyValue( value );
} catch ( const std::exception& exception ) {
return std::string( "<stringification failed: " ) +
exception.what() + ">";
} catch ( ... ) {
return "<stringification failed with a non-standard exception>";
}
}
} // namespace Detail
/// Runs independently seeded trials and greedily accepts failing shrink
/// candidates.
template <typename ValueType, typename Predicate>
requires std::invocable<Predicate&, const ValueType&>&&
std::convertible_to<std::invoke_result_t<Predicate&, const ValueType&>,
bool> [[nodiscard]] PropertyResult
CheckProperty( const Generator<ValueType>& generator,
Predicate predicate,
PropertyOptions options = {} ) {
if ( options.Trials == 0 ) {
return { PropertyStatus::kInvalidConfiguration,
0,
std::nullopt,
"Trials must be greater than zero" };
}
PropertyResult result;
for ( std::size_t trial = 0; trial < options.Trials; ++trial ) {
result.TrialsRun = trial + 1;
const std::uint64_t trialSeed =
Random::DeriveSeed( options.Seed, trial );
Random random( trialSeed );
std::optional<ValueType> sample;
try {
sample.emplace( generator.Generate( random ) );
} catch ( const std::exception& exception ) {
result.Status = PropertyStatus::kErrored;
result.Error =
std::string( "generator threw std::exception: " ) +
exception.what();
result.Failure = PropertyFailure{ options.Seed,
trialSeed,
trial + 1,
0,
"<not generated>",
result.Error };
return result;
} catch ( ... ) {
result.Status = PropertyStatus::kErrored;
result.Error = "generator threw a non-standard exception";
result.Failure = PropertyFailure{ options.Seed,
trialSeed,
trial + 1,
0,
"<not generated>",
result.Error };
return result;
}
auto reason = Detail::EvaluateProperty( predicate, *sample );
if ( !reason.has_value() ) { continue; }
std::size_t shrinkChecks = 0;
try {
bool improved = true;
while ( improved && shrinkChecks < options.MaxShrinkSteps ) {
improved = false;
const std::vector<ValueType> candidates =
generator.Shrink( *sample );
for ( std::size_t candidateIndex = 0;
candidateIndex < candidates.size();
++candidateIndex ) {
if ( shrinkChecks >= options.MaxShrinkSteps ) { break; }
++shrinkChecks;
const ValueType candidate = static_cast<ValueType>(
candidates[candidateIndex] );
auto candidateReason =
Detail::EvaluateProperty( predicate, candidate );
if ( candidateReason.has_value() ) {
sample.emplace( candidate );
reason = std::move( candidateReason );
improved = true;
break;
}
}
}
} catch ( const std::exception& exception ) {
result.Status = PropertyStatus::kErrored;
result.Error =
std::string( "shrinker threw std::exception: " ) +
exception.what();
result.Failure =
PropertyFailure{ options.Seed,
trialSeed,
trial + 1,
shrinkChecks,
Detail::DescribeValue( *sample ),
*reason };
return result;
} catch ( ... ) {
result.Status = PropertyStatus::kErrored;
result.Error = "shrinker threw a non-standard exception";
result.Failure =
PropertyFailure{ options.Seed,
trialSeed,
trial + 1,
shrinkChecks,
Detail::DescribeValue( *sample ),
*reason };
return result;
}
result.Status = PropertyStatus::kFailed;
result.Failure = PropertyFailure{ options.Seed,
trialSeed,
trial + 1,
shrinkChecks,
Detail::DescribeValue( *sample ),
*reason };
return result;
}
result.Status = PropertyStatus::kPassed;
return result;
}
} // namespace Progmasoft::Catch3
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