Anti-patterns
https://www.r-bloggers.com/unit-tests-for-r-packages/
References: 
testthat: Get Started with Testing @Article{testthat,
  author = {Hadley Wickham},
  journal = {The R Journal},
  month = {June},
  number = {1},
  pages = {5––10},
  title = {testthat: Get Started with Testing},
  url = {http://journal.r-project.org/archive/2011-1/RJournal_2011-1_Wickham.pdf},
  volume = {3},
  year = {2011},
  bdsk-url-1 = {http://journal.r-project.org/archive/2011-1/RJournal_2011-1_Wickham.pdf},
}
M. Burger, K. Juenemann, and T. Koenig. RUnit: R Unit test framework, 2009. URL http://CRAN. R-project.org/package=RUnit. R package ver- sion 0.4.22.
xUnit reference?