1  
 2  //              Copyright Catch2 Authors
 3  // Distributed under the Boost Software License, Version 1.0.
 4  //   (See accompanying file LICENSE.txt or copy at
 5  //        https://www.boost.org/LICENSE_1_0.txt)
 6  
 7  // SPDX-License-Identifier: BSL-1.0
 8  
 9  // 310-Gen-VariablesInGenerator.cpp
10  // Shows how to use variables when creating generators.
11  
12  // Note that using variables inside generators is dangerous and should
13  // be done only if you know what you are doing, because the generators
14  // _WILL_ outlive the variables -- thus they should be either captured
15  // by value directly, or copied by the generators during construction.
16  
17  #include <catch2/catch_test_macros.hpp>
18  #include <catch2/generators/catch_generators_adapters.hpp>
19  #include <catch2/generators/catch_generators_random.hpp>
20  
21  TEST_CASE("Generate random doubles across different ranges",
22            "[generator][example][advanced]") {
23      // Workaround for old libstdc++
24      using record = std::tuple<double, double>;
25      // Set up 3 ranges to generate numbers from
26      auto r = GENERATE(table<double, double>({
27          record{3, 4},
28          record{-4, -3},
29          record{10, 1000}
30      }));
31  
32      // This will not compile (intentionally), because it accesses a variable
33      // auto number = GENERATE(take(50, random(std::get<0>(r), std::get<1>(r))));
34  
35     // GENERATE_COPY copies all variables mentioned inside the expression
36     // thus this will work.
37      auto number = GENERATE_COPY(take(50, random(std::get<0>(r), std::get<1>(r))));
38  
39      REQUIRE(std::abs(number) > 0);
40  }
41  
42  // Compiling and running this file will result in 150 successful assertions
43