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94 lines
3.0 KiB
C++
94 lines
3.0 KiB
C++
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// Copyright Catch2 Authors
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE.txt or copy at
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// https://www.boost.org/LICENSE_1_0.txt)
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// SPDX-License-Identifier: BSL-1.0
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// 300-Gen-OwnGenerator.cpp
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// Shows how to define a custom generator.
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// Specifically we will implement a random number generator for integers
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// It will have infinite capacity and settable lower/upper bound
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#include <catch2/catch_test_macros.hpp>
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#include <catch2/generators/catch_generators.hpp>
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#include <catch2/generators/catch_generators_adapters.hpp>
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#include <random>
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namespace {
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// This class shows how to implement a simple generator for Catch tests
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class RandomIntGenerator final : public Catch::Generators::IGenerator<int> {
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std::minstd_rand m_rand;
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std::uniform_int_distribution<> m_dist;
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int current_number;
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public:
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RandomIntGenerator(int low, int high):
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m_rand(std::random_device{}()),
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m_dist(low, high)
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{
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static_cast<void>(next());
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}
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int const& get() const override;
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bool next() override {
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current_number = m_dist(m_rand);
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return true;
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}
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// Note: this improves the performance only a bit, but it is here
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// to show how you can override the skip functionality.
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void skipToNthElementImpl( std::size_t n ) override {
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auto current_index = currentElementIndex();
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assert(current_index <= n);
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// We cannot jump forward the underlying generator directly,
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// because we do not know how many bits each distributed number
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// would consume to be generated.
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for (; current_index < n; ++current_index) {
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(void)m_dist(m_rand);
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}
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// We do not have to touch the current element index; it is handled
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// by the base class.
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}
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};
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// Avoids -Wweak-vtables
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int const& RandomIntGenerator::get() const {
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return current_number;
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}
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// This helper function provides a nicer UX when instantiating the generator
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// Notice that it returns an instance of GeneratorWrapper<int>, which
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// is a value-wrapper around std::unique_ptr<IGenerator<int>>.
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Catch::Generators::GeneratorWrapper<int> random(int low, int high) {
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return Catch::Generators::GeneratorWrapper<int>(
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new RandomIntGenerator(low, high)
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// Another possibility:
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// Catch::Detail::make_unique<RandomIntGenerator>(low, high)
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);
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}
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} // end anonymous namespaces
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// The two sections in this test case are equivalent, but the first one
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// is much more readable/nicer to use
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TEST_CASE("Generating random ints", "[example][generator]") {
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SECTION("Nice UX") {
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auto i = GENERATE(take(100, random(-100, 100)));
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REQUIRE(i >= -100);
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REQUIRE(i <= 100);
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}
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SECTION("Creating the random generator directly") {
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auto i = GENERATE(take(100, GeneratorWrapper<int>(Catch::Detail::make_unique<RandomIntGenerator>(-100, 100))));
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REQUIRE(i >= -100);
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REQUIRE(i <= 100);
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}
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}
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// Compiling and running this file will result in 400 successful assertions
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