doctest
Fastest feature-rich C++11/14/17/20 single-header testing framework
...It brings the ability of compiled languages such as D / Rust / Nim to have tests written directly in the production code thanks to a fast, transparent and flexible test runner with a clean interface. The framework is and will stay free but needs your support to sustain its development. There are lots of new features and maintenance to do. There are many C++ testing frameworks - Catch, Boost.Test, UnitTest++, cpputest, googletest and others. The key differences between it and other testing frameworks are that it is light and unintrusive. Ultra light on compile times both in terms of including the header and writing thousands of asserts. ...