diff --git a/CMakeLists.txt b/CMakeLists.txt
index 41999ff..af1f48d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,4 @@
-# 3.8 version is required for `cxx_std_14`
+# 3.8 version is required for `cxx_std_17`
 cmake_minimum_required(VERSION 3.8 FATAL_ERROR)
 
 if(NOT DEFINED PROJECT_NAME)
@@ -9,7 +9,7 @@ project(promise.hpp)
 
 add_library(${PROJECT_NAME} INTERFACE)
 target_include_directories(${PROJECT_NAME} INTERFACE headers)
-target_compile_features(${PROJECT_NAME} INTERFACE cxx_std_14)
+target_compile_features(${PROJECT_NAME} INTERFACE cxx_std_17)
 
 if(BUILD_AS_STANDALONE)
     option(BUILD_WITH_UNTESTS "Build with unit tests" ON)
diff --git a/headers/promise.hpp/invoke.hpp b/headers/promise.hpp/invoke.hpp
deleted file mode 100644
index b75657f..0000000
--- a/headers/promise.hpp/invoke.hpp
+++ /dev/null
@@ -1,248 +0,0 @@
-/*******************************************************************************
- * This file is part of the "https://github.com/blackmatov/invoke.hpp"
- * For conditions of distribution and use, see copyright notice in LICENSE.md
- * Copyright (C) 2018-2019, by Matvey Cherevko (blackmatov@gmail.com)
- ******************************************************************************/
-
-#pragma once
-
-#include <tuple>
-#include <utility>
-#include <functional>
-#include <type_traits>
-
-#define INVOKE_HPP_NOEXCEPT_RETURN(...) \
-    noexcept(noexcept(__VA_ARGS__)) { return __VA_ARGS__; }
-
-#define INVOKE_HPP_NOEXCEPT_DECLTYPE_RETURN(...) \
-    noexcept(noexcept(__VA_ARGS__)) -> decltype (__VA_ARGS__) { return __VA_ARGS__; }
-
-//
-// void_t
-//
-
-namespace invoke_hpp
-{
-    namespace impl
-    {
-        template < typename... Args >
-        struct make_void {
-            using type = void;
-        };
-    }
-
-    template < typename... Args >
-    using void_t = typename impl::make_void<Args...>::type;
-}
-
-//
-// is_reference_wrapper
-//
-
-namespace invoke_hpp
-{
-    namespace impl
-    {
-        template < typename T >
-        struct is_reference_wrapper_impl
-        : std::false_type {};
-
-        template < typename U >
-        struct is_reference_wrapper_impl<std::reference_wrapper<U>>
-        : std::true_type {};
-    }
-
-    template < typename T >
-    struct is_reference_wrapper
-    : impl::is_reference_wrapper_impl<std::remove_cv_t<T>> {};
-}
-
-//
-// invoke
-//
-
-namespace invoke_hpp
-{
-    namespace impl
-    {
-        //
-        // invoke_member_object_impl
-        //
-
-        template
-        <
-            typename Base, typename F, typename Derived,
-            typename std::enable_if_t<std::is_base_of<Base, std::decay_t<Derived>>::value, int> = 0
-        >
-        constexpr auto invoke_member_object_impl(F Base::* f, Derived&& ref)
-        INVOKE_HPP_NOEXCEPT_DECLTYPE_RETURN(
-            std::forward<Derived>(ref).*f)
-
-        template
-        <
-            typename Base, typename F, typename RefWrap,
-            typename std::enable_if_t<is_reference_wrapper<std::decay_t<RefWrap>>::value, int> = 0
-        >
-        constexpr auto invoke_member_object_impl(F Base::* f, RefWrap&& ref)
-        INVOKE_HPP_NOEXCEPT_DECLTYPE_RETURN(
-            ref.get().*f)
-
-        template
-        <
-            typename Base, typename F, typename Pointer,
-            typename std::enable_if_t<
-                !std::is_base_of<Base, std::decay_t<Pointer>>::value &&
-                !is_reference_wrapper<std::decay_t<Pointer>>::value
-            , int> = 0
-        >
-        constexpr auto invoke_member_object_impl(F Base::* f, Pointer&& ptr)
-        INVOKE_HPP_NOEXCEPT_DECLTYPE_RETURN(
-            (*std::forward<Pointer>(ptr)).*f)
-
-        //
-        // invoke_member_function_impl
-        //
-
-        template
-        <
-            typename Base, typename F, typename Derived, typename... Args,
-            typename std::enable_if_t<std::is_base_of<Base, std::decay_t<Derived>>::value, int> = 0
-        >
-        constexpr auto invoke_member_function_impl(F Base::* f, Derived&& ref, Args&&... args)
-        INVOKE_HPP_NOEXCEPT_DECLTYPE_RETURN(
-            (std::forward<Derived>(ref).*f)(std::forward<Args>(args)...))
-
-        template
-        <
-            typename Base, typename F, typename RefWrap, typename... Args,
-            typename std::enable_if_t<is_reference_wrapper<std::decay_t<RefWrap>>::value, int> = 0
-        >
-        constexpr auto invoke_member_function_impl(F Base::* f, RefWrap&& ref, Args&&... args)
-        INVOKE_HPP_NOEXCEPT_DECLTYPE_RETURN(
-            (ref.get().*f)(std::forward<Args>(args)...))
-
-        template
-        <
-            typename Base, typename F, typename Pointer, typename... Args,
-            typename std::enable_if_t<
-                !std::is_base_of<Base, std::decay_t<Pointer>>::value &&
-                !is_reference_wrapper<std::decay_t<Pointer>>::value
-            , int> = 0
-        >
-        constexpr auto invoke_member_function_impl(F Base::* f, Pointer&& ptr, Args&&... args)
-        INVOKE_HPP_NOEXCEPT_DECLTYPE_RETURN(
-            ((*std::forward<Pointer>(ptr)).*f)(std::forward<Args>(args)...))
-    }
-
-    template
-    <
-        typename F, typename... Args,
-        typename std::enable_if_t<!std::is_member_pointer<std::decay_t<F>>::value, int> = 0
-    >
-    constexpr auto invoke(F&& f, Args&&... args)
-    INVOKE_HPP_NOEXCEPT_DECLTYPE_RETURN(
-        std::forward<F>(f)(std::forward<Args>(args)...))
-
-    template
-    <
-        typename F, typename T,
-        typename std::enable_if_t<std::is_member_object_pointer<std::decay_t<F>>::value, int> = 0
-    >
-    constexpr auto invoke(F&& f, T&& t)
-    INVOKE_HPP_NOEXCEPT_DECLTYPE_RETURN(
-        impl::invoke_member_object_impl(std::forward<F>(f), std::forward<T>(t)))
-
-    template
-    <
-        typename F, typename... Args,
-        typename std::enable_if_t<std::is_member_function_pointer<std::decay_t<F>>::value, int> = 0
-    >
-    constexpr auto invoke(F&& f, Args&&... args)
-    INVOKE_HPP_NOEXCEPT_DECLTYPE_RETURN(
-        impl::invoke_member_function_impl(std::forward<F>(f), std::forward<Args>(args)...))
-}
-
-//
-// invoke_result
-//
-
-namespace invoke_hpp
-{
-    namespace impl
-    {
-        struct invoke_result_impl_tag {};
-
-        template < typename Void, typename F, typename... Args >
-        struct invoke_result_impl {};
-
-        template < typename F, typename... Args >
-        struct invoke_result_impl<void_t<invoke_result_impl_tag, decltype(invoke_hpp::invoke(std::declval<F>(), std::declval<Args>()...))>, F, Args...> {
-            using type = decltype(invoke_hpp::invoke(std::declval<F>(), std::declval<Args>()...));
-        };
-    }
-
-    template < typename F, typename... Args >
-    struct invoke_result
-    : impl::invoke_result_impl<void, F, Args...> {};
-
-    template < typename F, typename... Args >
-    using invoke_result_t = typename invoke_result<F, Args...>::type;
-}
-
-//
-// is_invocable
-//
-
-namespace invoke_hpp
-{
-    namespace impl
-    {
-        struct is_invocable_r_impl_tag {};
-
-        template < typename Void, typename R, typename F, typename... Args >
-        struct is_invocable_r_impl
-        : std::false_type {};
-
-        template < typename R, typename F, typename... Args >
-        struct is_invocable_r_impl<void_t<is_invocable_r_impl_tag, invoke_result_t<F, Args...>>, R, F, Args...>
-        : std::conditional_t<
-            std::is_void<R>::value,
-            std::true_type,
-            std::is_convertible<invoke_result_t<F, Args...>, R>> {};
-    }
-
-    template < typename R, typename F, typename... Args >
-    struct is_invocable_r
-    : impl::is_invocable_r_impl<void, R, F, Args...> {};
-
-    template < typename F, typename... Args >
-    using is_invocable = is_invocable_r<void, F, Args...>;
-}
-
-//
-// apply
-//
-
-namespace invoke_hpp
-{
-    namespace impl
-    {
-        template < typename F, typename Tuple, std::size_t... I >
-        constexpr decltype(auto) apply_impl(F&& f, Tuple&& args, std::index_sequence<I...>)
-        INVOKE_HPP_NOEXCEPT_RETURN(
-            invoke_hpp::invoke(
-                std::forward<F>(f),
-                std::get<I>(std::forward<Tuple>(args))...))
-    }
-
-    template < typename F, typename Tuple >
-    constexpr decltype(auto) apply(F&& f, Tuple&& args)
-    INVOKE_HPP_NOEXCEPT_RETURN(
-        impl::apply_impl(
-            std::forward<F>(f),
-            std::forward<Tuple>(args),
-            std::make_index_sequence<std::tuple_size<std::decay_t<Tuple>>::value>()))
-}
-
-#undef INVOKE_HPP_NOEXCEPT_RETURN
-#undef INVOKE_HPP_NOEXCEPT_DECLTYPE_RETURN
diff --git a/headers/promise.hpp/jobber.hpp b/headers/promise.hpp/jobber.hpp
index 958f850..a398aca 100644
--- a/headers/promise.hpp/jobber.hpp
+++ b/headers/promise.hpp/jobber.hpp
@@ -6,22 +6,6 @@
 
 #pragma once
 
-#include <cstdint>
-#include <cassert>
-
-#include <tuple>
-#include <mutex>
-#include <atomic>
-#include <thread>
-#include <chrono>
-#include <memory>
-#include <vector>
-#include <utility>
-#include <exception>
-#include <stdexcept>
-#include <type_traits>
-#include <condition_variable>
-
 #include "promise.hpp"
 
 namespace jobber_hpp
@@ -58,7 +42,7 @@ namespace jobber_hpp
             std::size_t>;
 
         template < typename F, typename... Args >
-        using async_invoke_result_t = invoke_hpp::invoke_result_t<
+        using async_invoke_result_t = std::invoke_result_t<
             std::decay_t<F>,
             std::decay_t<Args>...>;
 
@@ -378,7 +362,7 @@ namespace jobber_hpp
     template < typename R, typename F, typename... Args >
     void jobber::concrete_task<R, F, Args...>::run() noexcept {
         try {
-            R value = invoke_hpp::apply(std::move(f_), std::move(args_));
+            R value = std::apply(std::move(f_), std::move(args_));
             promise_.resolve(std::move(value));
         } catch (...) {
             promise_.reject(std::current_exception());
@@ -408,7 +392,7 @@ namespace jobber_hpp
     template < typename F, typename... Args >
     void jobber::concrete_task<void, F, Args...>::run() noexcept {
         try {
-            invoke_hpp::apply(std::move(f_), std::move(args_));
+            std::apply(std::move(f_), std::move(args_));
             promise_.resolve();
         } catch (...) {
             promise_.reject(std::current_exception());
diff --git a/headers/promise.hpp/promise.hpp b/headers/promise.hpp/promise.hpp
index cfa51d8..64cc29f 100644
--- a/headers/promise.hpp/promise.hpp
+++ b/headers/promise.hpp/promise.hpp
@@ -13,6 +13,7 @@
 #include <tuple>
 #include <mutex>
 #include <atomic>
+#include <thread>
 #include <chrono>
 #include <memory>
 #include <vector>
@@ -24,8 +25,6 @@
 #include <type_traits>
 #include <condition_variable>
 
-#include "invoke.hpp"
-
 namespace promise_hpp
 {
     //
@@ -180,7 +179,7 @@ namespace promise_hpp
         }
 
         template < typename ResolveF
-                 , typename ResolveFR = invoke_hpp::invoke_result_t<ResolveF,T> >
+                 , typename ResolveFR = std::invoke_result_t<ResolveF,T> >
         std::enable_if_t<
             is_promise<ResolveFR>::value && std::is_void<typename ResolveFR::value_type>::value,
             promise<typename ResolveFR::value_type>>
@@ -191,7 +190,7 @@ namespace promise_hpp
                 n = next,
                 f = std::forward<ResolveF>(on_resolve)
             ](auto&& v) mutable {
-                auto np = invoke_hpp::invoke(
+                auto np = std::invoke(
                     std::forward<decltype(f)>(f),
                     std::forward<decltype(v)>(v));
                 std::move(np).then([n]() mutable {
@@ -207,7 +206,7 @@ namespace promise_hpp
         }
 
         template < typename ResolveF
-                 , typename ResolveFR = invoke_hpp::invoke_result_t<ResolveF,T> >
+                 , typename ResolveFR = std::invoke_result_t<ResolveF,T> >
         std::enable_if_t<
             is_promise<ResolveFR>::value && !std::is_void<typename ResolveFR::value_type>::value,
             promise<typename ResolveFR::value_type>>
@@ -218,7 +217,7 @@ namespace promise_hpp
                 n = next,
                 f = std::forward<ResolveF>(on_resolve)
             ](auto&& v) mutable {
-                auto np = invoke_hpp::invoke(
+                auto np = std::invoke(
                     std::forward<decltype(f)>(f),
                     std::forward<decltype(v)>(v));
                 std::move(np).then([n](auto&& nv) mutable {
@@ -238,7 +237,7 @@ namespace promise_hpp
             return then([
                 f = std::forward<ResolveF>(on_resolve)
             ](auto&& v) mutable {
-                auto r = invoke_hpp::invoke(
+                auto r = std::invoke(
                     std::forward<decltype(f)>(f),
                     std::forward<decltype(v)>(v));
                 return make_all_promise(std::move(r));
@@ -250,7 +249,7 @@ namespace promise_hpp
             return then([
                 f = std::forward<ResolveF>(on_resolve)
             ](auto&& v) mutable {
-                auto r = invoke_hpp::invoke(
+                auto r = std::invoke(
                     std::forward<decltype(f)>(f),
                     std::forward<decltype(v)>(v));
                 return make_race_promise(std::move(r));
@@ -262,7 +261,7 @@ namespace promise_hpp
             return then([
                 f = std::forward<ResolveF>(on_resolve)
             ](auto&& v) mutable {
-                auto r = invoke_hpp::invoke(
+                auto r = std::invoke(
                     std::forward<decltype(f)>(f),
                     std::forward<decltype(v)>(v));
                 return make_tuple_promise(std::move(r));
@@ -271,7 +270,7 @@ namespace promise_hpp
 
         template < typename ResolveF
                  , typename RejectF
-                 , typename ResolveFR = invoke_hpp::invoke_result_t<ResolveF,T> >
+                 , typename ResolveFR = std::invoke_result_t<ResolveF,T> >
         std::enable_if_t<
             !is_promise<ResolveFR>::value,
             promise<ResolveFR>>
@@ -286,7 +285,7 @@ namespace promise_hpp
         }
 
         template < typename ResolveF
-                 , typename ResolveFR = invoke_hpp::invoke_result_t<ResolveF,T> >
+                 , typename ResolveFR = std::invoke_result_t<ResolveF,T> >
         std::enable_if_t<
             !is_promise<ResolveFR>::value,
             promise<ResolveFR>>
@@ -443,7 +442,7 @@ namespace promise_hpp
                 ](std::exception_ptr e) mutable {
                     if ( has_reject ) {
                         try {
-                            invoke_hpp::invoke(
+                            std::invoke(
                                 std::forward<decltype(f)>(f),
                                 e);
                             n.resolve();
@@ -460,7 +459,7 @@ namespace promise_hpp
                     f = std::forward<ResolveF>(on_resolve)
                 ](auto&& v) mutable {
                     try {
-                        invoke_hpp::invoke(
+                        std::invoke(
                             std::forward<decltype(f)>(f),
                             std::forward<decltype(v)>(v));
                         n.resolve();
@@ -488,7 +487,7 @@ namespace promise_hpp
                 ](std::exception_ptr e) mutable {
                     if ( has_reject ) {
                         try {
-                            auto r = invoke_hpp::invoke(
+                            auto r = std::invoke(
                                 std::forward<decltype(f)>(f),
                                 e);
                             n.resolve(std::move(r));
@@ -505,7 +504,7 @@ namespace promise_hpp
                     f = std::forward<ResolveF>(on_resolve)
                 ](auto&& v) mutable {
                     try {
-                        auto r = invoke_hpp::invoke(
+                        auto r = std::invoke(
                             std::forward<decltype(f)>(f),
                             std::forward<decltype(v)>(v));
                         n.resolve(std::move(r));
@@ -521,11 +520,11 @@ namespace promise_hpp
             template < typename ResolveF, typename RejectF >
             void add_handlers_(ResolveF&& resolve, RejectF&& reject) {
                 if ( status_ == status::resolved ) {
-                    invoke_hpp::invoke(
+                    std::invoke(
                         std::forward<ResolveF>(resolve),
                         storage_.value());
                 } else if ( status_ == status::rejected ) {
-                    invoke_hpp::invoke(
+                    std::invoke(
                         std::forward<RejectF>(reject),
                         exception_);
                 } else {
@@ -616,7 +615,7 @@ namespace promise_hpp
         }
 
         template < typename ResolveF
-                 , typename ResolveFR = invoke_hpp::invoke_result_t<ResolveF> >
+                 , typename ResolveFR = std::invoke_result_t<ResolveF> >
         std::enable_if_t<
             is_promise<ResolveFR>::value && std::is_void<typename ResolveFR::value_type>::value,
             promise<typename ResolveFR::value_type>>
@@ -627,7 +626,7 @@ namespace promise_hpp
                 n = next,
                 f = std::forward<ResolveF>(on_resolve)
             ]() mutable {
-                auto np = invoke_hpp::invoke(
+                auto np = std::invoke(
                     std::forward<decltype(f)>(f));
                 std::move(np).then([n]() mutable {
                     n.resolve();
@@ -642,7 +641,7 @@ namespace promise_hpp
         }
 
         template < typename ResolveF
-                 , typename ResolveFR = invoke_hpp::invoke_result_t<ResolveF> >
+                 , typename ResolveFR = std::invoke_result_t<ResolveF> >
         std::enable_if_t<
             is_promise<ResolveFR>::value && !std::is_void<typename ResolveFR::value_type>::value,
             promise<typename ResolveFR::value_type>>
@@ -653,7 +652,7 @@ namespace promise_hpp
                 n = next,
                 f = std::forward<ResolveF>(on_resolve)
             ]() mutable {
-                auto np = invoke_hpp::invoke(
+                auto np = std::invoke(
                     std::forward<decltype(f)>(f));
                 std::move(np).then([n](auto&& nv) mutable {
                     n.resolve(std::forward<decltype(nv)>(nv));
@@ -672,7 +671,7 @@ namespace promise_hpp
             return then([
                 f = std::forward<ResolveF>(on_resolve)
             ]() mutable {
-                auto r = invoke_hpp::invoke(
+                auto r = std::invoke(
                     std::forward<decltype(f)>(f));
                 return make_all_promise(std::move(r));
             });
@@ -683,7 +682,7 @@ namespace promise_hpp
             return then([
                 f = std::forward<ResolveF>(on_resolve)
             ]() mutable {
-                auto r = invoke_hpp::invoke(
+                auto r = std::invoke(
                     std::forward<decltype(f)>(f));
                 return make_race_promise(std::move(r));
             });
@@ -694,7 +693,7 @@ namespace promise_hpp
             return then([
                 f = std::forward<ResolveF>(on_resolve)
             ]() mutable {
-                auto r = invoke_hpp::invoke(
+                auto r = std::invoke(
                     std::forward<decltype(f)>(f));
                 return make_tuple_promise(std::move(r));
             });
@@ -702,7 +701,7 @@ namespace promise_hpp
 
         template < typename ResolveF
                  , typename RejectF
-                 , typename ResolveFR = invoke_hpp::invoke_result_t<ResolveF> >
+                 , typename ResolveFR = std::invoke_result_t<ResolveF> >
         std::enable_if_t<
             !is_promise<ResolveFR>::value,
             promise<ResolveFR>>
@@ -717,7 +716,7 @@ namespace promise_hpp
         }
 
         template < typename ResolveF
-                 , typename ResolveFR = invoke_hpp::invoke_result_t<ResolveF> >
+                 , typename ResolveFR = std::invoke_result_t<ResolveF> >
         std::enable_if_t<
             !is_promise<ResolveFR>::value,
             promise<ResolveFR>>
@@ -869,7 +868,7 @@ namespace promise_hpp
                 ](std::exception_ptr e) mutable {
                     if ( has_reject ) {
                         try {
-                            invoke_hpp::invoke(
+                            std::invoke(
                                 std::forward<decltype(f)>(f),
                                 e);
                             n.resolve();
@@ -886,7 +885,7 @@ namespace promise_hpp
                     f = std::forward<ResolveF>(on_resolve)
                 ]() mutable {
                     try {
-                        invoke_hpp::invoke(
+                        std::invoke(
                             std::forward<decltype(f)>(f));
                         n.resolve();
                     } catch (...) {
@@ -913,7 +912,7 @@ namespace promise_hpp
                 ](std::exception_ptr e) mutable {
                     if ( has_reject ) {
                         try {
-                            auto r = invoke_hpp::invoke(
+                            auto r = std::invoke(
                                 std::forward<decltype(f)>(f),
                                 e);
                             n.resolve(std::move(r));
@@ -930,7 +929,7 @@ namespace promise_hpp
                     f = std::forward<ResolveF>(on_resolve)
                 ]() mutable {
                     try {
-                        auto r = invoke_hpp::invoke(
+                        auto r = std::invoke(
                             std::forward<decltype(f)>(f));
                         n.resolve(std::move(r));
                     } catch (...) {
@@ -945,10 +944,10 @@ namespace promise_hpp
             template < typename ResolveF, typename RejectF >
             void add_handlers_(ResolveF&& resolve, RejectF&& reject) {
                 if ( status_ == status::resolved ) {
-                    invoke_hpp::invoke(
+                    std::invoke(
                         std::forward<ResolveF>(resolve));
                 } else if ( status_ == status::rejected ) {
-                    invoke_hpp::invoke(
+                    std::invoke(
                         std::forward<RejectF>(reject),
                         exception_);
                 } else {
@@ -1032,7 +1031,7 @@ namespace promise_hpp
         };
 
         try {
-            invoke_hpp::invoke(
+            std::invoke(
                 std::forward<F>(f),
                 std::move(resolver),
                 std::move(rejector));
diff --git a/headers/promise.hpp/scheduler.hpp b/headers/promise.hpp/scheduler.hpp
index 93a17bf..7ace422 100644
--- a/headers/promise.hpp/scheduler.hpp
+++ b/headers/promise.hpp/scheduler.hpp
@@ -6,21 +6,6 @@
 
 #pragma once
 
-#include <cstdint>
-#include <cassert>
-
-#include <tuple>
-#include <mutex>
-#include <atomic>
-#include <chrono>
-#include <memory>
-#include <vector>
-#include <utility>
-#include <exception>
-#include <stdexcept>
-#include <type_traits>
-#include <condition_variable>
-
 #include "promise.hpp"
 
 namespace scheduler_hpp
@@ -57,7 +42,7 @@ namespace scheduler_hpp
             std::size_t>;
 
         template < typename F, typename... Args >
-        using schedule_invoke_result_t = invoke_hpp::invoke_result_t<
+        using schedule_invoke_result_t = std::invoke_result_t<
             std::decay_t<F>,
             std::decay_t<Args>...>;
 
@@ -286,7 +271,7 @@ namespace scheduler_hpp
     template < typename R, typename F, typename... Args >
     void scheduler::concrete_task<R, F, Args...>::run() noexcept {
         try {
-            R value = invoke_hpp::apply(std::move(f_), std::move(args_));
+            R value = std::apply(std::move(f_), std::move(args_));
             promise_.resolve(std::move(value));
         } catch (...) {
             promise_.reject(std::current_exception());
@@ -316,7 +301,7 @@ namespace scheduler_hpp
     template < typename F, typename... Args >
     void scheduler::concrete_task<void, F, Args...>::run() noexcept {
         try {
-            invoke_hpp::apply(std::move(f_), std::move(args_));
+            std::apply(std::move(f_), std::move(args_));
             promise_.resolve();
         } catch (...) {
             promise_.reject(std::current_exception());
diff --git a/untests/invoke_tests.cpp b/untests/invoke_tests.cpp
deleted file mode 100644
index 0190028..0000000
--- a/untests/invoke_tests.cpp
+++ /dev/null
@@ -1,510 +0,0 @@
-/*******************************************************************************
- * This file is part of the "https://github.com/blackmatov/invoke.hpp"
- * For conditions of distribution and use, see copyright notice in LICENSE.md
- * Copyright (C) 2018-2019, by Matvey Cherevko (blackmatov@gmail.com)
- ******************************************************************************/
-
-#define CATCH_CONFIG_FAST_COMPILE
-#include <catch2/catch.hpp>
-
-#include <promise.hpp/invoke.hpp>
-namespace inv = invoke_hpp;
-
-namespace
-{
-    void simple_static_function() {
-    }
-
-    int simple_static_function_r() {
-        return 42;
-    }
-
-    int simple_static_function_r_with_arg(int v) {
-        return v;
-    }
-
-    const int& simple_static_function_r_with_ref_arg(const int& v) {
-        return v;
-    }
-
-    class obj_t {
-    public:
-        int value = 42;
-        const int value_c = 42;
-
-        void member() {
-        }
-
-        int member_r() {
-            return 42;
-        }
-
-        int member_r_with_arg(int v) {
-            return v;
-        }
-
-        const int& member_r_with_ref_arg(const int& v) {
-            return v;
-        }
-    };
-
-    class obj2_t {
-    };
-}
-
-TEST_CASE("invoke"){
-    SECTION("invoke_functions"){
-        inv::invoke(simple_static_function);
-        REQUIRE(inv::invoke(simple_static_function_r) == 42);
-        REQUIRE(inv::invoke(simple_static_function_r_with_arg, 42) == 42);
-        {
-            int v = 42;
-            REQUIRE(&inv::invoke(simple_static_function_r_with_ref_arg, v) == &v);
-        }
-    }
-    SECTION("invoke_members"){
-        obj_t o;
-
-        inv::invoke(&obj_t::member, o);
-        inv::invoke(&obj_t::member, &o);
-        inv::invoke(&obj_t::member, std::ref(o));
-
-        REQUIRE(inv::invoke(&obj_t::member_r, o) == 42);
-        REQUIRE(inv::invoke(&obj_t::member_r, &o) == 42);
-        REQUIRE(inv::invoke(&obj_t::member_r, std::ref(o)) == 42);
-
-        REQUIRE(inv::invoke(&obj_t::member_r_with_arg, o, 42) == 42);
-        REQUIRE(inv::invoke(&obj_t::member_r_with_arg, &o, 42) == 42);
-        REQUIRE(inv::invoke(&obj_t::member_r_with_arg, std::ref(o), 42) == 42);
-
-        {
-            int v = 42;
-            REQUIRE(&inv::invoke(&obj_t::member_r_with_ref_arg, o, std::ref(v)) == &v);
-            REQUIRE(&inv::invoke(&obj_t::member_r_with_ref_arg, &o, std::ref(v)) == &v);
-            REQUIRE(&inv::invoke(&obj_t::member_r_with_ref_arg, std::ref(o), std::ref(v)) == &v);
-        }
-    }
-    SECTION("invoke_member_objects"){
-        obj_t o;
-
-        REQUIRE(inv::invoke(&obj_t::value, o) == 42);
-        REQUIRE(inv::invoke(&obj_t::value, &o) == 42);
-        REQUIRE(inv::invoke(&obj_t::value, std::ref(o)) == 42);
-
-        REQUIRE(inv::invoke(&obj_t::value_c, o) == 42);
-        REQUIRE(inv::invoke(&obj_t::value_c, &o) == 42);
-        REQUIRE(inv::invoke(&obj_t::value_c, std::ref(o)) == 42);
-    }
-}
-
-TEST_CASE("invoke_result"){
-    SECTION("invoke_result_functions"){
-        static_assert(
-            std::is_same<
-                void,
-                inv::invoke_result_t<decltype(simple_static_function)>>::value,
-            "unit test fail");
-        static_assert(
-            std::is_same<
-                int,
-                inv::invoke_result_t<decltype(simple_static_function_r)>>::value,
-            "unit test fail");
-        static_assert(
-            std::is_same<
-                int,
-                inv::invoke_result_t<decltype(simple_static_function_r_with_arg), int>>::value,
-            "unit test fail");
-        static_assert(
-            std::is_same<
-                const int&,
-                inv::invoke_result_t<decltype(simple_static_function_r_with_ref_arg), const int&>>::value,
-            "unit test fail");
-    }
-    SECTION("invoke_result_members"){
-        static_assert(
-            std::is_same<void,
-                inv::invoke_result_t<decltype(&obj_t::member), obj_t>>::value,
-            "unit test fail");
-        static_assert(
-            std::is_same<void,
-                inv::invoke_result_t<decltype(&obj_t::member), obj_t*>>::value,
-            "unit test fail");
-        static_assert(
-            std::is_same<void,
-                inv::invoke_result_t<decltype(&obj_t::member), std::reference_wrapper<obj_t>>>::value,
-            "unit test fail");
-
-        static_assert(
-            std::is_same<int,
-                inv::invoke_result_t<decltype(&obj_t::member_r), obj_t>>::value,
-            "unit test fail");
-        static_assert(
-            std::is_same<int,
-                inv::invoke_result_t<decltype(&obj_t::member_r), obj_t*>>::value,
-            "unit test fail");
-        static_assert(
-            std::is_same<int,
-                inv::invoke_result_t<decltype(&obj_t::member_r), std::reference_wrapper<obj_t>>>::value,
-            "unit test fail");
-
-        static_assert(
-            std::is_same<int,
-                inv::invoke_result_t<decltype(&obj_t::member_r_with_arg), obj_t, int>>::value,
-            "unit test fail");
-        static_assert(
-            std::is_same<int,
-                inv::invoke_result_t<decltype(&obj_t::member_r_with_arg), obj_t*, int>>::value,
-            "unit test fail");
-        static_assert(
-            std::is_same<int,
-                inv::invoke_result_t<decltype(&obj_t::member_r_with_arg), std::reference_wrapper<obj_t>, int>>::value,
-            "unit test fail");
-
-        static_assert(
-            std::is_same<const int&,
-                inv::invoke_result_t<decltype(&obj_t::member_r_with_ref_arg), obj_t, const int&>>::value,
-            "unit test fail");
-        static_assert(
-            std::is_same<const int&,
-                inv::invoke_result_t<decltype(&obj_t::member_r_with_ref_arg), obj_t*, const int&>>::value,
-            "unit test fail");
-        static_assert(
-            std::is_same<const int&,
-                inv::invoke_result_t<decltype(&obj_t::member_r_with_ref_arg), std::reference_wrapper<obj_t>, const int&>>::value,
-            "unit test fail");
-    }
-}
-
-TEST_CASE("is_invocable"){
-    SECTION("is_invocable_functions"){
-        static_assert(
-            inv::is_invocable<decltype(simple_static_function)>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable<decltype(simple_static_function_r)>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable<decltype(simple_static_function_r_with_arg), int>::value,
-            "unit test fail");
-    }
-    SECTION("is_not_invocable_functions"){
-        static_assert(
-            !inv::is_invocable<decltype(simple_static_function), int>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable<decltype(simple_static_function_r), obj_t>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable<decltype(simple_static_function_r_with_arg)>::value,
-            "unit test fail");
-    }
-    SECTION("is_invocable_members"){
-        static_assert(
-            inv::is_invocable<decltype(&obj_t::member), obj_t>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable<decltype(&obj_t::member), obj_t*>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable<decltype(&obj_t::member), std::reference_wrapper<obj_t>>::value,
-            "unit test fail");
-
-        static_assert(
-            inv::is_invocable<decltype(&obj_t::member_r), obj_t>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable<decltype(&obj_t::member_r), obj_t*>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable<decltype(&obj_t::member_r), std::reference_wrapper<obj_t>>::value,
-            "unit test fail");
-
-        static_assert(
-            inv::is_invocable<decltype(&obj_t::member_r_with_arg), obj_t, int>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable<decltype(&obj_t::member_r_with_arg), obj_t*, int>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable<decltype(&obj_t::member_r_with_arg), std::reference_wrapper<obj_t>, int>::value,
-            "unit test fail");
-    }
-    SECTION("is_not_invocable_members"){
-        static_assert(
-            !inv::is_invocable<decltype(&obj_t::member)>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable<decltype(&obj_t::member), int>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable<decltype(&obj_t::member), std::reference_wrapper<obj_t>*>::value,
-            "unit test fail");
-
-        static_assert(
-            !inv::is_invocable<decltype(&obj_t::member_r), obj_t**>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable<decltype(&obj_t::member_r), obj2_t*>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable<decltype(&obj_t::member_r), std::reference_wrapper<obj2_t>>::value,
-            "unit test fail");
-
-        static_assert(
-            !inv::is_invocable<decltype(&obj_t::member_r_with_arg), obj_t, char*>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable<decltype(&obj_t::member_r_with_arg), obj_t*>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable<decltype(&obj_t::member_r_with_arg), std::reference_wrapper<obj2_t>, int>::value,
-            "unit test fail");
-    }
-    SECTION("is_invocable_objects"){
-        static_assert(
-            inv::is_invocable<decltype(&obj_t::value), obj_t>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable<decltype(&obj_t::value), obj_t*>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable<decltype(&obj_t::value), std::reference_wrapper<obj_t>>::value,
-            "unit test fail");
-
-        static_assert(
-            inv::is_invocable<decltype(&obj_t::value_c), obj_t>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable<decltype(&obj_t::value_c), obj_t*>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable<decltype(&obj_t::value_c), std::reference_wrapper<obj_t>>::value,
-            "unit test fail");
-    }
-    SECTION("is_not_invocable_objects"){
-        static_assert(
-            !inv::is_invocable<decltype(&obj_t::value)>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable<decltype(&obj_t::value), obj2_t*>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable<decltype(&obj_t::value), obj_t, int>::value,
-            "unit test fail");
-
-        static_assert(
-            !inv::is_invocable<decltype(&obj_t::value_c), obj_t**>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable<decltype(&obj_t::value_c), obj_t*, obj_t*>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable<decltype(&obj_t::value_c), std::reference_wrapper<obj_t**>>::value,
-            "unit test fail");
-    }
-}
-
-TEST_CASE("is_invocable_r"){
-    SECTION("is_invocable_r_functions"){
-        static_assert(
-            inv::is_invocable_r<void, decltype(simple_static_function)>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable_r<int, decltype(simple_static_function_r)>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable_r<void, decltype(simple_static_function_r)>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable_r<const int&, decltype(simple_static_function_r_with_arg), const int&>::value,
-            "unit test fail");
-    }
-    SECTION("is_not_invocable_r_functions"){
-        static_assert(
-            !inv::is_invocable_r<void, decltype(simple_static_function), int>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable_r<int, decltype(simple_static_function_r), obj_t>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable_r<const int&, decltype(simple_static_function_r_with_arg), const obj2_t&>::value,
-            "unit test fail");
-
-        static_assert(
-            !inv::is_invocable_r<int, decltype(simple_static_function)>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable_r<int*, decltype(simple_static_function_r)>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable_r<obj_t, decltype(simple_static_function_r_with_arg), const int&>::value,
-            "unit test fail");
-    }
-    SECTION("is_invocable_r_members"){
-        static_assert(
-            inv::is_invocable_r<void, decltype(&obj_t::member), obj_t>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable_r<void, decltype(&obj_t::member), obj_t*>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable_r<void, decltype(&obj_t::member), std::reference_wrapper<obj_t>>::value,
-            "unit test fail");
-
-        static_assert(
-            inv::is_invocable_r<int, decltype(&obj_t::member_r), obj_t>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable_r<int, decltype(&obj_t::member_r), obj_t*>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable_r<int, decltype(&obj_t::member_r), std::reference_wrapper<obj_t>>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable_r<void, decltype(&obj_t::member_r), std::reference_wrapper<obj_t>>::value,
-            "unit test fail");
-
-        static_assert(
-            inv::is_invocable_r<int, decltype(&obj_t::member_r_with_arg), obj_t, int>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable_r<int, decltype(&obj_t::member_r_with_arg), obj_t*, int>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable_r<int, decltype(&obj_t::member_r_with_arg), std::reference_wrapper<obj_t>, int>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable_r<void, decltype(&obj_t::member_r_with_arg), std::reference_wrapper<obj_t>, int>::value,
-            "unit test fail");
-    }
-    SECTION("is_not_invocable_r_members"){
-        static_assert(
-            !inv::is_invocable_r<int, decltype(&obj_t::member), obj_t>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable_r<int*, decltype(&obj_t::member), obj_t*>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable_r<obj_t, decltype(&obj_t::member), std::reference_wrapper<obj_t>>::value,
-            "unit test fail");
-
-        static_assert(
-            !inv::is_invocable_r<obj_t, decltype(&obj_t::member_r), obj_t>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable_r<int*, decltype(&obj_t::member_r), obj_t*>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable_r<int, decltype(&obj_t::member_r), std::reference_wrapper<obj2_t>>::value,
-            "unit test fail");
-
-        static_assert(
-            !inv::is_invocable_r<obj_t, decltype(&obj_t::member_r_with_arg), obj_t, int>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable_r<int*, decltype(&obj_t::member_r_with_arg), obj_t*, int>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable_r<int, decltype(&obj_t::member_r_with_arg), std::reference_wrapper<obj_t>, obj2_t>::value,
-            "unit test fail");
-    }
-    SECTION("is_invocable_r_objects"){
-        static_assert(
-            inv::is_invocable_r<int, decltype(&obj_t::value), obj_t>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable_r<int, decltype(&obj_t::value), obj_t*>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable_r<int, decltype(&obj_t::value), std::reference_wrapper<obj_t>>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable_r<void, decltype(&obj_t::value), std::reference_wrapper<obj_t>>::value,
-            "unit test fail");
-
-        static_assert(
-            inv::is_invocable_r<int, decltype(&obj_t::value_c), obj_t>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable_r<int, decltype(&obj_t::value_c), obj_t*>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable_r<int, decltype(&obj_t::value_c), std::reference_wrapper<obj_t>>::value,
-            "unit test fail");
-        static_assert(
-            inv::is_invocable_r<void, decltype(&obj_t::value_c), std::reference_wrapper<obj_t>>::value,
-            "unit test fail");
-    }
-    SECTION("is_not_invocable_r_objects"){
-        static_assert(
-            !inv::is_invocable_r<obj_t, decltype(&obj_t::value), obj_t>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable_r<int*, decltype(&obj_t::value), obj_t*>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable_r<int, decltype(&obj_t::value), std::reference_wrapper<obj_t>, obj2_t>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable_r<void, decltype(&obj_t::value), std::reference_wrapper<obj_t>, obj2_t>::value,
-            "unit test fail");
-
-        static_assert(
-            !inv::is_invocable_r<obj_t, decltype(&obj_t::value_c), obj_t>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable_r<int*, decltype(&obj_t::value_c), obj_t*>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable_r<obj2_t, decltype(&obj_t::value_c), std::reference_wrapper<obj_t>>::value,
-            "unit test fail");
-        static_assert(
-            !inv::is_invocable_r<void, decltype(&obj_t::value_c), std::reference_wrapper<obj_t**>>::value,
-            "unit test fail");
-    }
-}
-
-TEST_CASE("apply"){
-    SECTION("apply_functions"){
-        inv::apply(simple_static_function, std::make_tuple());
-        REQUIRE(inv::apply(simple_static_function_r, std::make_tuple()) == 42);
-        REQUIRE(inv::apply(simple_static_function_r_with_arg, std::make_tuple(42)) == 42);
-        {
-            int v = 42;
-            REQUIRE(&inv::apply(simple_static_function_r_with_ref_arg, std::make_tuple(std::ref(v))) == &v);
-        }
-    }
-    SECTION("apply_members"){
-        obj_t o;
-
-        inv::apply(&obj_t::member, std::make_tuple(o));
-        inv::apply(&obj_t::member, std::make_tuple(&o));
-        inv::apply(&obj_t::member, std::make_tuple(std::ref(o)));
-
-        REQUIRE(inv::apply(&obj_t::member_r, std::make_tuple(o)) == 42);
-        REQUIRE(inv::apply(&obj_t::member_r, std::make_tuple(&o)) == 42);
-        REQUIRE(inv::apply(&obj_t::member_r, std::make_tuple(std::ref(o))) == 42);
-
-        REQUIRE(inv::apply(&obj_t::member_r_with_arg, std::make_tuple(o, 42)) == 42);
-        REQUIRE(inv::apply(&obj_t::member_r_with_arg, std::make_tuple(&o, 42)) == 42);
-        REQUIRE(inv::apply(&obj_t::member_r_with_arg, std::make_tuple(std::ref(o), 42)) == 42);
-
-        {
-            int v = 42;
-            REQUIRE(&inv::apply(&obj_t::member_r_with_ref_arg, std::make_tuple(o, std::ref(v))) == &v);
-            REQUIRE(&inv::apply(&obj_t::member_r_with_ref_arg, std::make_tuple(&o, std::ref(v))) == &v);
-            REQUIRE(&inv::apply(&obj_t::member_r_with_ref_arg, std::make_tuple(std::ref(o), std::ref(v))) == &v);
-        }
-    }
-    SECTION("apply_member_objects"){
-        obj_t o;
-
-        REQUIRE(inv::apply(&obj_t::value, std::make_tuple(o)) == 42);
-        REQUIRE(inv::apply(&obj_t::value, std::make_tuple(&o)) == 42);
-        REQUIRE(inv::apply(&obj_t::value, std::make_tuple(std::ref(o))) == 42);
-
-        REQUIRE(inv::apply(&obj_t::value_c, std::make_tuple(o)) == 42);
-        REQUIRE(inv::apply(&obj_t::value_c, std::make_tuple(&o)) == 42);
-        REQUIRE(inv::apply(&obj_t::value_c, std::make_tuple(std::ref(o))) == 42);
-    }
-}