blob: 96840bbbe47b62af6b141ece5190332c9c14f401 [file] [log] [blame]
// 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;
RandomDoubleGenerator(double low, double high):
m_dist(low, high)
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