Flaky subscribe test #6399
Description
Issue Description
Sometimes there is a test failure in CI:
13> #115 failed: Subscribe_test.cpp(1053)
/usr/local/include/c++/15.2.0/bits/stl_vector.h:1370: constexpr std::vector<_Tp, _Alloc>::reference std::vector<_Tp, _Alloc>::back() [with _Tp = std::tuple<int, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, int>; _Alloc = std::allocator<std::tuple<int, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, int> >; reference = std::tuple<int, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool, int>&]: Assertion '!this->empty()' failed.
An example of such failure in CI.
Steps to Reproduce
It's not obvious so far how to reproduce this, but it looks like the failure happens when using gcc 15 on Linux in debug more with code coverage.
Expected Result
Test passes.
Actual Result
Sometimes test fails.