A whole package

2019-08-04

This vignette will teach you how to create a unit test shell for all of the examples in an entire package’s documentation.

Setup

First, let’s set up a dummy package called tempkg with just the detect.R and match.R files from the source code of the stringr package.

usethis::create_package("tempkg", open = FALSE)
fs::file_copy(
  system.file("extdata", c("detect.R", "match.R"), package = "exampletestr"), 
  "tempkg/R/" 
)

Now let’s move into the tempkg directory:

setwd("tempkg/")

and set the active project:

usethis::proj_set(".")

The detect.R file looks like this (well, I’ve abbreviated it slightly):

#' Detect the presence or absence of a pattern in a string.
#'
#' Vectorised over `string` and `pattern`.
#'
#' @param string Input vector. Either a character vector, or something
#'  coercible to one.
#' @param pattern Pattern to look for.
#'
#' @return A logical vector.
#' 
#' @export
#' @examples
#' fruit <- c("apple", "banana", "pear", "pinapple")
#' str_detect(fruit, "a")
#' str_detect(fruit, "^a")
#' str_detect(fruit, "a$")
#' str_detect(fruit, "b")
#' str_detect(fruit, "[aeiou]")
#'
str_detect <- function(string, pattern) {
  switch(type(pattern),
         empty = ,
         bound = str_count(string, pattern) > 0,
         fixed = stri_detect_fixed(string, pattern, opts_fixed = opts(pattern)),
         coll  = stri_detect_coll(string,  pattern, opts_collator = opts(pattern)),
         regex = stri_detect_regex(string, pattern, opts_regex = opts(pattern))
  )
}

We can make a unit tests shell file for each .R file in the package using make_tests_shells_pkg():

make_tests_shells_pkg()

This outputs test-detect.R and test-match.R files in the tests/testthat folder. As an example of what to do next, the test-detect.R file has contents

test_that("`str_detect()` works", {
  fruit <- c("apple", "banana", "pear", "pinapple")
  expect_equal(str_detect(fruit, "a"), )
  expect_equal(str_detect(fruit, "^a"), )
  expect_equal(str_detect(fruit, "a$"), )
  expect_equal(str_detect(fruit, "b"), )
  expect_equal(str_detect(fruit, "[aeiou]"), )
  expect_equal(str_detect("aecfg", letters), )
})

which can be sensibly completed as

test_that("`str_detect()` works", {
  fruit <- c("apple", "banana", "pear", "pinapple")
  expect_equal(str_detect(fruit, "a"), rep(TRUE, 4))
  expect_equal(str_detect(fruit, "^a"), c(TRUE, rep(FALSE, 3)))
  expect_equal(str_detect(fruit, "a$"), c(FALSE, TRUE, FALSE, FALSE))
  expect_equal(str_detect(fruit, "b"), c(FALSE, TRUE, FALSE, FALSE))
  expect_equal(str_detect(fruit, "[aeiou]"), rep(TRUE, 4))
  expect_equal(str_detect("aecfg", letters), 
               letters %in% c("a", "c", "e", "f", "g"))
})

test-match.R must similarly be completed.

knitr::opts_knit$set(root.dir = tempdir(check = TRUE))
if (fs::dir_exists("tempkg")) fs::dir_delete("tempkg")
knitr::opts_knit$set(root.dir = init_wd)