Add a promise mock

include/continuable/continuable-base.hpp

@@ -1334,7 +1334,7 @@ constexpr auto common_result_of(Signature signature, signature_hint_tag<>,
 
 /// Determine the common result between all continuation which are chained
 /// with an `any` strategy, consider two continuations:
-/// c1 with `void(int)` and c22 with `void(float)`, the common result shared
+/// c1 with `void(int)` and c2 with `void(float)`, the common result shared
 /// between both continuations is `void(int)`.
 template <typename Signature, typename First, typename... Args>
 constexpr auto common_result_of(Signature signature, First first,

test/mock/test-mock.cpp

@@ -55,6 +55,22 @@ template <typename... T> struct promise {
   bool is_canceled() const noexcept { return false; }
 };
 
+template <typename... T> struct promise {
+  void set_value(T...) noexcept {}
+
+  void operator()(T...) && noexcept {}
+
+  void set_exception(std::exception_ptr exception) noexcept {
+    // ...
+    (void)exception;
+  }
+
+  void set_error(std::error_code error) noexcept {
+    // ...
+    (void)error;
+  }
+};
+
 template <typename... Result> struct accumulator {
   auto accumulate() {
     return [] {};