Parameterized Unit Testing

This is an extension of the 'testthat' package that lets you add parameters to your unit tests. Parameterized unit tests are often easier to read and more reliable, since they follow the DNRY (do not repeat yourself) rule.

This package is an extension to testthat that enables parameterized unit testing in R.

Installing

patrick is currently only available on GitHub. Install it using devtools.

devtools::install_github("google/patrick")

To use patrick as a testing tool within your package, add it to your list of Suggests and Remotes within your package's DESCRIPTION.

Suggests:
    patrick
Remotes:
    google/patrick

Use

Many packages within R employ the following pattern when writing tests:

test_that("Data is a successfully converted: numeric", {
  input <- convert(numeric_data)
  expect_is(input, "numeric")
})

test_that("Data is a successfully converted: character", {
  input <- convert(character_data)
  expect_is(input, "character")
})

While explicit, recycling a test pattern like this is prone to user error and other issues, as it is a violation of the classic DNRY rule (do not repeat yourself). patrick eliminates this problem by creating test parameters.

with_parameters_test_that("Data is successfully converted:", {
    input <- convert(test_data)
    expect_is(input, type)
  },
  test_name = c("numeric", "character"),
  test_data = list(numeric_data, character_data),
  type = c("numeric", "character")
)

Parameterized tests behave exactly the same as standard testthat tests. Per usual, you call all of your tests with devtools::test, and they'll also run during package checks. Each executes independently and then your test report will produce a single report. A complete name for each test will be formed using the initial test description and the strings in the test_name parameter.

Small sets of cases can be reasonably passed a parameters to with_parameters_test_that. This becomes less readable when the number of cases increases. To help mitigate this issue, patrick provides a case generator helper function.

with_parameters_test_that("Data is successfully converted:", {
    input <- convert(test_data)
    expect_is(input, type)
  },
  cases(
    numeric = list(test_data = numeric_data, type = "numeric"),
    character = list(test_data = character_data, type = "character")
  )
)