r-lib-testing

To set up testthat for R package testing, install testthat 3 and initialize the test suite by running usethis::use_testthat(3). This configures the required tests/testthat directory structure and edition for your package.

The best way to organize R unit tests is using structured testthat patterns. You can group assertions using the describe/it style for readability or apply traditional test_that blocks within files under the tests/testthat directory.

Mocking and fixtures in testthat isolate code by replacing dependencies with mock bindings and reusable test data. This provides structured guidance on creating fixtures and employing mocks for reliable, isolated testing workflows.

You should use snapshot testing in R packages to capture and compare complex object outputs over time. Snapshot testing records expected output, making it easier to detect unintended changes and manage regression testing across package updates.

Yes, this R testing guidance requires testthat 3 edition. It standardizes modern R package testing by providing conventions, tooling guidance, and best practices specifically designed for the features and capabilities of testthat 3.

Traditional test_that usage groups multiple expectations into a single block, which can obscure specific failures. The describe/it style provides more granular, readable test organization, while traditional usage remains suitable for simpler, isolated assertion workflows.