R CMD check automatically runs tests located in tests/ directory. However running the tests this way requires building the package first. After that R CMD check goes through various different sanity checks before finally reaching the tests at the end.
Question: Is there a way to run those tests without having to build or install the package first?
NOTE: without using testthat or other non-standard packages.
To summarise our discussion.
R CMD check for unit testing provided by base R R/ (and dyn.load everything under source/) and then source everything under tests/ (actually, I also use the Example sections of the help pages in the man/ directory as test cases and compare their outcome to those from previous package versions)I assume that these are the basic testing functionalities provided by devtools and testthat. If you expect to develop multiple packages and want to stay independent from non-base-R, I'd recommed to automate the above processes with custom scripts/packages.
I'd recomment looking into http://r-pkgs.had.co.nz/tests.html.