C++ compile-time first / macro free unit-testing

Compile-time first unit-testing is a super power of modern C++.

It catches errors earlier and helps (to a certain degree) avoiding memory leaks and undefined behaviors. However, the main problem facing compile-time tests are bad error messages. With C++20 and, especially, with clang that can be improved a lot to a degree sometimes even better than at run-time. Running tests at compile-time is useful and more and more powerful with each new standard, but there is also a strong case for run-time execution as well. Firstly, not all tests can be executed at compile-time due to constexpr limitations (for example goto/exceptions/reinterpret_cast/... in C++20). Additionally there is case for the code coverage, debugging and CI reporting. Therefore, the combination of both seems the most powerful: compile-time tests with nicer error messages and run-time execution on top (with ability to choose the execution model globally and/or for specific tests).

https://github.com/boost-ext/ut2 is trying to accomplish just that.