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

Defines unit test log formatter interface.

You can define a class with implements this interface and use an instance of it as a Unit Test Framework log formatter

namespace boost {
  namespace unit_test {
    struct log_checkpoint_data;
    struct log_entry_data;

    class unit_test_log_formatter;
  }
}