| // 310-Gen-VariablesInGenerator.cpp |
| // Shows how to use variables when creating generators. |
| |
| // Note that using variables inside generators is dangerous and should |
| // be done only if you know what you are doing, because the generators |
| // _WILL_ outlive the variables -- thus they should be either captured |
| // by value directly, or copied by the generators during construction. |
| |
| #include <catch2/catch.hpp> |
| |
| #include <random> |
| |
| // Lets start by implementing a parametrizable double generator |
| class RandomDoubleGenerator : public Catch::Generators::IGenerator<double> { |
| std::minstd_rand m_rand; |
| std::uniform_real_distribution<> m_dist; |
| double current_number; |
| public: |
| |
| RandomDoubleGenerator(double low, double high): |
| m_rand(std::random_device{}()), |
| m_dist(low, high) |
| { |
| static_cast<void>(next()); |
| } |
| |
| double const& get() const override; |
| bool next() override { |
| current_number = m_dist(m_rand); |
| return true; |
| } |
| }; |
| |
| // Avoids -Wweak-vtables |
| double const& RandomDoubleGenerator::get() const { |
| return current_number; |
| } |
| |
| |
| // Also provide a nice shortcut for creating the generator |
| Catch::Generators::GeneratorWrapper<double> random(double low, double high) { |
| return Catch::Generators::GeneratorWrapper<double>(std::unique_ptr<Catch::Generators::IGenerator<double>>(new RandomDoubleGenerator(low, high))); |
| } |
| |
| |
| TEST_CASE("Generate random doubles across different ranges", |
| "[generator][example][advanced]") { |
| // Workaround for old libstdc++ |
| using record = std::tuple<double, double>; |
| // Set up 3 ranges to generate numbers from |
| auto r = GENERATE(table<double, double>({ |
| record{3, 4}, |
| record{-4, -3}, |
| record{10, 1000} |
| })); |
| |
| // This will not compile (intentionally), because it accesses a variable |
| // auto number = GENERATE(take(50, random(r.first, r.second))); |
| |
| // We have to manually register the generators instead |
| // Notice that we are using value capture in the lambda, to avoid lifetime issues |
| auto number = Catch::Generators::generate( CATCH_INTERNAL_LINEINFO, |
| [=]{ |
| using namespace Catch::Generators; |
| return makeGenerators(take(50, random(std::get<0>(r), std::get<1>(r)))); |
| } |
| ); |
| REQUIRE(std::abs(number) > 0); |
| } |
| |
| // Compiling and running this file will result in 150 successful assertions |
| |