Where to place library calls with testthat?

Question

I am looking for best practice help with the brilliant testthat. Where is the best place to put your library(xyzpackage) calls to use all the package functionality?

I first have been setting up a runtest.R setting up paths and packages. I then run test_files(test-code.R) which only holds context and tests. Example for structure follows:

# runtests.R
library(testthat)
library(data.table)

source("code/plotdata-fun.R")

mytestreport <- test_file("code/test-plotdata.R")

# does other stuff like append date and log test report (not shown)

and in my test files e.g. test-plotdata.R (a stripped down version):

#my tests for plotdata
context("Plot Chart")

test_that("Inputs valid", {

  test.dt  = data.table(px = c(1,2,3), py = c(1,4,9))
  test.notdt <- c(1,2,3)

  # illustrating the check for data table as first param in my code
  expect_error(PlotMyStandardChart(test.notdt, 
                                   plot.me = FALSE),
                "Argument must be data table/frame")

  # then do other tests with test.dt etc...
})

1. Is this the way @hadley intended it to be used? It is not clear from the journal article. Should I also be duplicating library calls in my test files as well? Do you need a library set up in each context, or just one at start of file?

2. Is it okay to over-call library(package) in r?

3. To use the test_dir() and other functionality what is best way to set up your files. I do use require() in my functions, but I also set up test data examples in the contexts. (In above example, you will see I would need data.table package for test.dt to use in other tests).

Thanks for your help.

Answer 1

Some suggestions / comments:

• set up each file so that it can be run on its own with test_file without additional setup. This way you can easily run an individual file while developing if you are just focusing on one small part of a larger project (useful if running all your tests is slow)
• there is little penalty to calling library multiple times as that function first checks to see if the package is already attached
• if you set up each file so that it can be run with test_file, then test_dir will work fine without having to do anything additional
• you don't need to library(testthat) in any of your test files since presumably you are running them with test_file or test_dir, which would require testthat to be loaded

Also, you can just look at one of Hadley's recent packages to see how he does it (e.g. dplyr tests).