Make auto_test_package work with C++ tests

[Yuri-M-Dias]

Hello, and thanks for the for awesome package!
I was wondering if there's any way to make the autotest function work with C++ tests too? I used use_catch() to add the tests to my project, however I need to rerun the tests for the C++ part manually, and can't rely on autotest for that.

From what I can gleam in the code (here) , it's not made for looking anywhere else that isn't tests/ and R/, so I don't think that there's a way of doing this now, correct? I can submit a PR for this if it's desirable/the correct place to do so.

[hadley]

It looks like this should be a fairly straightforward modification to auto_test_package() to add file.path(pkg$path, "src") to code_path if it exists. Do you want to have a go at implementing this?