macros for async tests with catch2, boost cobalt

async_test_main.hpp

// header for include in test.cpp files
//
// [public domain]
//
// usage:
//
// - include this source file in test_async.cpp, ...
//
// - in test_async.cpp, ... define any one or more sections like as follows:
//
//     ASYNC_TEST_CASE("name...") { /* coroutine... */ } 
//
//   ... along with any non-async TEST_CASE or other Catch2 test macros
//
//   The ASYNC_TEST_CASE macro should serve as mostly a drop-in replacement
//   for Catch2 TEST_CASE, with the added feature of the test body representing
//   a coroutine. The coroutine will be run within a cobalt::task<void> via
//   cobalt::spawn, using Boost Cobalt.
//
// - use TEST_MAIN() at the end of the source file, thus ensuring Cobalt's
//   co_main will be used when running the file's catch2 tests
//
// - Link swith Boost::cobalt, Catch2::Catch2, ...
//
// - Known limitation: No support for test tags in this ASYNC_TEST_CASE
//
// - Known limitation: When the actual test code is included within
//   each cobalt::task<void> section, the output from catch2 at the 
//   command line may not accurately represent the number of test 
//   assertions in each async test1
//
// cmake e.g:
//
// find_package(Catch2 3.0.0 REQUIRED)
// include(Catch)
//
// find_package(Boost REQUIRED COMPONENTS system)
// find_package(Boost REQUIRED CONFIG COMPONENTS asio cobalt preprocessor)
//
// add_executable(test_async test_async.cpp)
// taget_link_libraries(test_async PRIVATE 
//    Boost::system Boost::asio Boost::cobalt 
//    Boost::preprocessor Catch2::Catch2
// )
// target_include_directories(test_async PRIVATE
//  ${ANY_VAR}/any_directory_containing_this_file/)
// catch_discover_tests(test_async)

#pragma once

#include <boost/asio/io_context.hpp>
#include <boost/asio/use_future.hpp>
#include <boost/cobalt/main.hpp>
#include <boost/cobalt/task.hpp>
#include <boost/cobalt/this_thread.hpp>
#include <boost/cobalt/spawn.hpp>
#include <boost/preprocessor/cat.hpp>
#include <catch2/catch_session.hpp>
#include <catch2/catch_test_macros.hpp>

// NOLINTBEGIN(misc-unused-alias-decls)
namespace asio = boost::asio;
namespace cobalt = boost::cobalt;
namespace sys = boost::system;
// NOLINTEND(misc-unused-alias-decls)


#ifndef ASYNC_TEST_CASE
#    define ASYNC_TEST_CASE(_name, ...)                                                  \
        cobalt::task<void> BOOST_PP_CAT(test_task_, __LINE__)();                         \
        TEST_CASE(_name) {                                                               \
            asio::io_context ctx{BOOST_ASIO_CONCURRENCY_HINT_1};                         \
            auto exec = ctx.get_executor();                                              \
            cobalt::this_thread::set_executor(exec);                                     \
                                                                                         \
            auto ftr = cobalt::spawn(ctx, BOOST_PP_CAT(test_task_, __LINE__)(),          \
                                     asio::use_future);                                  \
            ctx.run();                                                                   \
            ftr.wait();                                                                  \
        }                                                                                \
        cobalt::task<void> BOOST_PP_CAT(test_task_, __LINE__)()
#endif


#ifndef TEST_MAIN
#    define TEST_MAIN(...)                                                               \
       cobalt::main co_main(int argc, char* argv[]) {                                    \
            __VA_ARGS__                                                                  \
            co_return Catch::Session{}.run(argc, argv);                                  \
        }
#endif