make the counter update thread-safe

Author: daixtrose

polymorphism/test/include/test_polymorphism/mocking.hpp

@@ -1,6 +1,7 @@
 #ifndef POLYMORPHISM_MOCKING_HPP
 #define POLYMORPHISM_MOCKING_HPP
 
+#include <atomic>
 #include <cstddef>
 #include <list>
 #include <string>
@@ -9,7 +10,7 @@ namespace mocking {
 
 struct Mock {
     std::list<std::string> collectedSetArguments;
-    mutable std::size_t numberOfCallsToCoolFeature { 0 };
+    mutable std::atomic<std::size_t> numberOfCallsToCoolFeature { 0 };
 
     std::string coolFeature() const
     {

polymorphism/test/src/test_consume.cpp

@@ -56,15 +56,15 @@ int main()
             when("I pass it to a function that expects an argument that fulfils the constraints") = [&] {
                 auto result = modern::consume(impl);
 
-                then("set() should be called twice") = [=] {
+                then("set() should be called twice") = [&] {
                     expect(EXPECTED_COOLFEATURE_CALLS == impl.numberOfCallsToCoolFeature);
                 };
 
                 then("the answer to all questions should be given") = [=] {
                     expect("The answer to all questions is 42"s == result);
                 };
 
-                then("the state of the argument should be modified as a side effect") = [=] {
+                then("the state of the argument should be modified as a side effect") = [&] {
                     expect("42"s == impl.coolFeature());
                 };
             };