cppmp/test/cppmp/cppmp_generic_predicate_tests.cpp

#include <gtest/gtest.h>

#include <cppmp/misc/generic_predicate.h>

template<typename X, typename = void>
struct builder
{
    using is_default = cppmp::true_t;

    template<typename... T_args>
    static constexpr decltype(auto) apply(T_args&&...)
        { static_assert(sizeof...(T_args) == -1, "Invalid parameters for build(...)!"); }
};

template<>
struct builder<
    cppmp::list<int>,
    void>
{
    static constexpr decltype(auto) apply(int i)
        { return i; }
};

constexpr decltype(auto) build = cppmp::generic_predicate<builder> { };

static_assert(
    !decltype(build)::is_valid<void>::value,
    "Expected build to be invalid");

static_assert(
    decltype(build)::is_valid<int>::value,
    "Expected build to be valid");

TEST(generic_predicate_tests, simple)
{
    auto i = build(5);

    EXPECT_EQ(5, i);
}