...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
Invokes the test using the specified runner.
template< class = void> void operator()( runner& r);
Data members are set up here instead of the constructor as a convenience to writing the derived class to avoid repetition of forwarded constructor arguments to the base. Normally this is called by the framework for you.