I am trying to understand how to use datasets with the boost.test library. I am following the documentation here <http://www.boost.org/doc/libs/1_65_1/libs/test/doc/html/boost_test/tests_organization/test_cases/test_case_generation/datasets.html> and have created my dataset as follows: namespace bdata = boost::unit_test::data; struct test_set { class iterator { int m_a; public: iterator() : m_a(0){} void operator++() { ++m_a; } int operator*() const { return m_a; } }; using sample = int; enum {arity = 1}; auto begin() const { return iterator{}; } bdata::size_t size() const { return 5; // let's assume only 5 numbers } }; namespace boost { namespace unit_test { namespace data { namespace monomorphic { template <> struct is_dataset<test_set> : std::true_type{}; }}}} which is very simple and iterates numbers from 0 to 4. The following simple test compiles and runs just fine: // this works as expected and prints 0, 1, 2, 3, 4 BOOST_DATA_TEST_CASE( example_test1, test_set(), my_datum) { std::cout << my_datum << std::endl; } However, when I try to zip <http://www.boost.org/doc/libs/1_65_1/libs/test/doc/html/boost_test/tests_organization/test_cases/test_case_generation/operations.html#boost_test.tests_organization.test_cases.test_case_generation.operations.zips> two such datasets it fails to compile (Apple LLVM version 9.0.0 (clang-900.0.38)): // error: invalid operands to binary expression ('typename data::result_of::make<test_set>::type' (aka 'test_set') and 'test_set') test_set() ^ test_set(), // ~~~~~~~~~~~^~~~~~~~~~~~~ BOOST_DATA_TEST_CASE( example_test2, test_set() ^ test_set(), my_datum1, my_datum2) { std::cout << my_datum1 << " " << my_datum2 << std::endl; } Is what I am trying to do legal? If so, what is the correct way to achieve it? Thank you for your help! Live code here <https://wandbox.org/permlink/6CI286mynvVCjQdW>