Chapter 8 Tests

Tests are really important to a healthy package.

Some people even start off with tests! 😮 see TDD, or “test driven development”

8.1 test infrastructure

8.1.1 Exercise: set up test infrastructure

Create manually, or run

usethis::use_testthat()

which:

• creates tests/testthat.R
• creates tests/testthat/
• adds testthat package as a Suggested package

8.2 write some tests

8.2.1 Exercise: write tests

Run

usethis::use_test('file-name')

Or create a file in tests/testthat/ of the form test-foobar.R

Within the test file, if you ran use_test() you’ll have something like:

context("test-stuff")

test_that("multiplication works", {
  expect_equal(2 * 2, 4)
})

Add a test like that above if you don’t have it already.

8.3 run tests

8.3.1 Exercise: run tests

from the command line

Rscript -e 'devtools::test()'

from R

devtools::test()

Or buttons in IDE

8.4 structure of a test file

• context states the overall goal of the file, e.g., tests for function helloworld
  • context can be repeated whenever you like
  • context are the things printed when you run tests
• test_that blocks, or function calls, can have any code run and at least one test expectation, e.g., expect_equal

8.5 further reading

the tests chapter