Consider this:

/// document foo
void foo(int) {...}

void foo(string) {...}

///
unittest
{
    // use foo like this!
    foo(1);
}

The unit test is not included in the documentation, because foo(string) was not ditto'd. But clearly, the unit test was supposed to be part of the documentation.

I propose we make a documented unit test that isn't attached to any symbol a warning when generating documentation.