catch2/examples/300-Gen-OwnGenerator.cpp

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// 300-Gen-OwnGenerator.cpp
// Shows how to define a custom generator.
// Specifically we will implement a random number generator for integers
// It will have infinite capacity and settable lower/upper bound
2020-01-21 14:46:07 +01:00
#include <catch2/catch_test_macros.hpp>
#include <catch2/generators/catch_generators.hpp>
#include <catch2/generators/catch_generators_adapters.hpp>
#include <random>
namespace {
// This class shows how to implement a simple generator for Catch tests
class RandomIntGenerator : public Catch::Generators::IGenerator<int> {
std::minstd_rand m_rand;
std::uniform_int_distribution<> m_dist;
int current_number;
public:
RandomIntGenerator(int low, int high):
m_rand(std::random_device{}()),
m_dist(low, high)
{
static_cast<void>(next());
}
int const& get() const override;
bool next() override {
current_number = m_dist(m_rand);
return true;
}
};
// Avoids -Wweak-vtables
int const& RandomIntGenerator::get() const {
return current_number;
}
// This helper function provides a nicer UX when instantiating the generator
// Notice that it returns an instance of GeneratorWrapper<int>, which
// is a value-wrapper around std::unique_ptr<IGenerator<int>>.
Catch::Generators::GeneratorWrapper<int> random(int low, int high) {
return Catch::Generators::GeneratorWrapper<int>(
new RandomIntGenerator(low, high)
// Another possibility:
// Catch::Detail::make_unique<RandomIntGenerator>(low, high)
);
}
} // end anonymous namespaces
// The two sections in this test case are equivalent, but the first one
// is much more readable/nicer to use
TEST_CASE("Generating random ints", "[example][generator]") {
SECTION("Nice UX") {
auto i = GENERATE(take(100, random(-100, 100)));
REQUIRE(i >= -100);
REQUIRE(i <= 100);
}
SECTION("Creating the random generator directly") {
auto i = GENERATE(take(100, GeneratorWrapper<int>(Catch::Detail::make_unique<RandomIntGenerator>(-100, 100))));
REQUIRE(i >= -100);
REQUIRE(i <= 100);
}
}
// Compiling and running this file will result in 400 successful assertions