boost unit test cartesian product of mpl list

Question

Suppose I have two mpl lists, say

typedef boost::mpl::list<int, double> inner_types;
typedef boost::mpl::list<std::vector, std::set> outer_types;

I was hoping to be able, in a boost unit test, to iterate over the cartesian product of these lists and construct an object from each combination..something like the following:

BOOST_TEST_CASE_TEMPLATE(mytest, InnerType, inner_types, OuterType, outer_types) {
    OuterType<InnerType> obj;

    BOOST_CHECK(ns::foo(obj));
}

but it seems like you can only have one mpl list when using _TEMPLATE for a boost test case. Is there a way to achieve what I am intending?

Answer 1

You could use Boost MP11 similar to this to merge merge the two lists to a single Cartesian product as follows

#include <boost/mp11.hpp>

template <template <typename...> typename... F>
using mp_list_q = boost::mp11::mp_list<boost::mp11::mp_quote<F>...>;

using outer_types = mp_list_q<std::vector, std::set>;
using inner_types = boost::mp11::mp_list<int, double>;

using TypeList = boost::mp11::mp_product<boost::mp11::mp_invoke_q,  
                                         outer_types, 
                                         inner_types>;

In this example TypeList corresponds to:

boost::mp11::mp_list<std::vector<int>, std::vector<double>, std::set<int>, std::set<double>>

This could then be used in a typed unit test as follows:

BOOST_TEST_CASE_TEMPLATE_FUNCTION(foo_test, T) {
  BOOST_TEST(ns::foo(T{}) == true);
}

boost::unit_test::test_suite* init_unit_test_suite(int, char* []) {
  boost::unit_test::framework::master_test_suite().add(BOOST_TEST_CASE_TEMPLATE(foo_test, TypeList));
  return EXIT_SUCCESS;
}

Try it here!

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If for some reason you can't use Boost MP11 you could write yourself a manual solution with variadic templates to create the alias TypeList similar to the one I have written here.