blob: c8b6a65df71758c3c43e1a717dcda7a18d8e3845 [file] [log] [blame]
// 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
#include <catch2/catch.hpp>
#include <random>
// 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;
RandomIntGenerator(int low, int high):
m_dist(low, high)
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>(std::unique_ptr<Catch::Generators::IGenerator<int>>(new RandomIntGenerator(low, high)));
// 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>(std::unique_ptr<IGenerator<int>>(new RandomIntGenerator(-100, 100)))));
REQUIRE(i >= -100);
REQUIRE(i <= 100);
// Compiling and running this file will result in 400 successful assertions