Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

This is an older version of Boost and was released in 2021. The current version is 1.89.0.

unit_test::suite_results::failed

Returns the number of failures.

std::size_t
failed() const;