Introducing patrick
This package is an extension to testthat that enables parameterized unit
testing in R.
Installing
The release version of patrick is available on CRAN. Install it in the usual
manner:
install.packages("patrick")
The development version of 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 within your package's DESCRIPTION.
Suggests:
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_type(input, "double")
})
test_that("Data is a successfully converted: character", {
input <- convert(character_data)
expect_type(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_type(input, type)
},
test_data = list(numeric_data, character_data),
type = c("double", "character"),
.test_name = type
)
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 as 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_type(input, type)
},
cases(
double = list(test_data = numeric_data, type = "double"),
character = list(test_data = character_data, type = "character")
)
)
More complicated testing cases can be constructed using data frames. This is
usually best handled within a helper function and in a helper-<test>.R file.
make_cases <- function() {
tibble::tribble(
~ .test_name, ~ expr, ~ numeric_value,
"sin", sin(pi / 4), 1 / sqrt(2),
"cos", cos(pi / 4), 1 / sqrt(2),
"tan", tan(pi / 4), 1
)
}
with_parameters_test_that(
"trigonometric functions match identities",
{
testthat::expect_equal(expr, numeric_value)
},
.cases = make_cases()
)
If you don't provide test names when generating cases, patrick will generate
them automatically from the test data.
Inspiration
This package is inspired by parameterized testing packages in other languages,
notably the parameterized library
in Python.
Contributing
Please read the
CONTRIBUTING.md
for details on how to contribute to this project.
Disclaimer
This is not an officially supported Google product.
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