Considering adding helper file for data loading in `testthat/` or using `withr` package functionalities

[Melkiades]

I was reading this nice post, and I have already solved the library issues in PR #359. This follows @gmbecker comment#PR359 for suggested package. Here, I argue that it could be better to move the test data into a testthat/helper-fakedata.R file and keep the library in a testthat/setup-suggested_libraries.R file. I am open to discussing any idea which might involve withr.

• [ ] Completely remove :: from tests.
• [ ] Move data loading to testthat/helper-fakedata.R and rename setup file with only libraries loads.
• [ ] Discuss if it is worth using withr.