KevCaz's Website

Over the past few weeks, I took some time to review the unit tests for rmangal and rcites. Both packages are R clients for web APIs:

  • rmangal allows users to search ecological interactions available in the Mangal database;
  • rcites allows users to query the Species+ database by leveraging the Speciesplus/CITES Checklist API.

One of the main challenges with such packages is to not get archived on CRAN đŸ˜±! rmangal was actually archived a year ago for policy violation on internet access, and so one of my main goals was to get it back on CRAN. I was relatively aware of ways to avoid using the Internet on CRAN as I had already used vcr for a small project, but I clearly needed to learn more to use it efficiently. Fortunately, MaĂ«lle Salmon had been working on a very useful book on the topic, HTTP testing in R, that has a lot of valuable advice that helped me design my tests with vcr!

Below is a code chunk that exemplifies how I proceeded

tx_id <- 4521
test_that("spp_cites_legislation() scope & language works", {
  vcr::use_cassette("spp_cites_legislation_sco", {
    res <- spp_cites_legislation(taxon_id = tx_id, scope = 'all', 
      language = 'fr', verbose = FALSE)
  expect_s3_class(res, "spp_cites_leg")
  expect_true("Guinée" %in% res$cites_suspensions$

Basically, I created blocs of tests (initiated by test_that()) around one request. Every request (or sometimes, a couple of requests) had its own cassette (vcr::use_cassette()) followed by the tests associated (expect_*(...)). In the example above, I do one request to access CITES appendix listings and reservations for the taxon 4521, which actually is the African bush elephant (Loxodonta africana). Then I test whether I get the right class (line 7) and whether the output has some expected features given the parameters I passed to spp_cites_legislation(). Specifically, I know that all entries of $cites_listings$is_current aren’t true because scope (time scope of legislation) is set to all so I test this (line 8). Also, given that I selected fr as language, I know that “GuinĂ©e” should be part of the geographical entities $cites_suspensions$ (Guinea with the French spelling), thus the line 9. If you want to see more, the unit tests for rmangal are available on GitHub ( and so are the tests for rcites (

Reviewing my unit tests was also an opportunity to learn a bit more about tests in general. Notably, I found out that I wasn’t testing the classes the right way! Wanna know why? Check out Martin Maechler’s blog post When you think class(.) == *, think again!. Now I use the dedicated function expect_s3_class(), which by the way has an exact parameter that I should have used! I probably will use it in future releases. I’ve also learned some features of testthat 3.0.0, especially the snapshot testing that is very useful to test messages! That’s another good learning.

That’s all folks!