Gabriel Dos Reis <gdr_at_[hidden]> writes:

> [Boris]
> > For example, the implementation partition may include a unit test
> > (because that's the only way to access the private parts) which
> > is registered with the test harness.
>
> How would that work in practice (concrete example)?

The following example works with GCC 12.

// file: tester.hxx
//
struct test_registrar
{
  static void (*test) ();
  explicit test_registrar (void (*t) ()) {test = t;}
};

// file: tester.cxx
//
#include "tester.hxx"

void (*test_registrar::test) ();

int main ()
{
  test_registrar::test ();
}

// file: hello-printer.mxx
//
module;
#include <cassert>
#include "tester.hxx"
module hello:print;

static void
unit_test ()
{
  assert (false);
}

test_registrar init (&unit_test);

// buidfile
//
exe{tester}: cxx{tester} mxx{hello-printer}