The **[future]** package defines the Future API which consists of a small number of functions for writing [R] code that can be evaluated either sequential or in parallel based a single setting without having to change anything in the code. Parallelization can be done via one of many backends, e.g. via built-in multicore, multisession and cluster backends (based on the **parallel** package) or via third-party backends such as **[future.batchtools]**, **[future.callr]** and **[future.mirai]**. The design motto of the Future API is: > Write once, run anywhere In order for such code to work regardless of which future backend the end-user choose, it is critical that the backend fully complies with the [Future API Backend Specification]. A future backend with a 100% compliance rate guarantees that the code will work equally well there as in sequential mode. This R package - **[future.tests]** - provides a test suite for validation that a future backend complies with the Future API.  ## Validate a Future Backend All future backends implementing the Future API should validate that they conform to the Future API. This can be done using the **[future.tests]** package, which provides two API for running the tests. The tests can be performed either from within R or from outside of R from the command line making it easy to include them package tests and in Continuous Integration (CI) pipelines. ### From Within R ```r > results <- future.tests::check(plan = "multisession") > exit_code <- attr(results, "exit_code") > if (exit_code != 0) stop("One or more tests failed") ``` ### From Outside R ```sh $ Rscript -e future.tests::check --test-plan="multisession" $ exit_code=$? $ [[ exit_code -eq 0 ]] || { >&2 echo "One or more tests failed"; exit 1; } ``` [R]: https://www.r-project.org [future]: https://future.futureverse.org [future.batchtools]: https://future.batchtools.futureverse.org [future.callr]: https://future.callr.futureverse.org [future.mirai]: https://future.mirai.futureverse.org [future.tests]: https://future.tests.futureverse.org [Future API Backend Specification]: https://future.futureverse.org/articles/future-6-future-api-backend-specification.html