tests/testthat.R, and adds the testthat package
to the Suggests field. Learn more in https://r-pkgs.org/tests.html
use_testthat(edition = NULL, parallel = FALSE)
testthat edition to use. Defaults to the latest edition, i.e. the major version number of the currently installed testthat.
Should tests be run in parallel? This feature appeared in testthat 3.0.0; see https://testthat.r-lib.org/articles/parallel.html for details and caveats.
use_test() to create individual test files