Not sure if this is recommended for testing purposes, but you can try using
`:::'; e.g., mypkg:::invisibleFunction(...).
Andy
> From: Paul Roebuck
>
> How do you get around the problem of having tests for
> functions that are not exported in NAMESPACE? It seems
> rather self-defeating to have to export everything so
> that 'R CMD CHECK pkg' won't crash when it encounters
> a test case for an internal function. I don't want
> someone using the package to call the function, but the
> package itself should be able to see its own contents.
>
> ----------------------------------------------------------
> SIGSIG -- signature too long (core dumped)