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Add the necessary infrastructure to enable C++ unit testing in R packages with Catch and testthat.


use_catch(dir = getwd())



The directory containing an R package.


Calling use_catch() will:

  1. Create a file src/test-runner.cpp, which ensures that the testthat package will understand how to run your package's unit tests,

  2. Create an example test file src/test-example.cpp, which showcases how you might use Catch to write a unit test,

  3. Add a test file tests/testthat/test-cpp.R, which ensures that testthat will run your compiled tests during invocations of devtools::test() or R CMD check, and

  4. Create a file R/catch-routine-registration.R, which ensures that R will automatically register this routine when tools::package_native_routine_registration_skeleton() is invoked.

You will also need to:

  • Add xml2 to Suggests, with e.g. usethis::use_package("xml2", "Suggests")

  • Add testthat to LinkingTo, with e.g. usethis::use_package("testthat", "LinkingTo")

C++ unit tests can be added to C++ source files within the src directory of your package, with a format similar to R code tested with testthat. Here's a simple example of a unit test written with testthat + Catch:

context("C++ Unit Test") {
  test_that("two plus two is four") {
    int result = 2 + 2;
    expect_true(result == 4);

When your package is compiled, unit tests alongside a harness for running these tests will be compiled into your R package, with the C entry point run_testthat_tests(). testthat will use that entry point to run your unit tests when detected.


All of the functions provided by Catch are available with the CATCH_ prefix -- see here for a full list. testthat provides the following wrappers, to conform with testthat's R interface:

contextCATCH_TEST_CASEThe context of a set of tests.
test_thatCATCH_SECTIONA test section.
expect_trueCATCH_CHECKTest that an expression evaluates to true.
expect_falseCATCH_CHECK_FALSETest that an expression evalutes to false.
expect_errorCATCH_CHECK_THROWSTest that evaluation of an expression throws an exception.
expect_error_asCATCH_CHECK_THROWS_ASTest that evaluation of an expression throws an exception of a specific class.

In general, you should prefer using the testthat wrappers, as testthat also does some work to ensure that any unit tests within will not be compiled or run when using the Solaris Studio compilers (as these are currently unsupported by Catch). This should make it easier to submit packages to CRAN that use Catch.

Symbol Registration

If you've opted to disable dynamic symbol lookup in your package, then you'll need to explicitly export a symbol in your package that testthat can use to run your unit tests. testthat will look for a routine with one of the names:


See Controlling Visibility and Registering Symbols in the Writing R Extensions manual for more information.

Advanced Usage

If you'd like to write your own Catch test runner, you can instead use the testthat::catchSession() object in a file with the form:

#include <testthat.h>

void run()
    Catch::Session& session = testthat::catchSession();
    // interact with the session object as desired

This can be useful if you'd like to run your unit tests with custom arguments passed to the Catch session.

Standalone Usage

If you'd like to use the C++ unit testing facilities provided by Catch, but would prefer not to use the regular testthat R testing infrastructure, you can manually run the unit tests by inserting a call to:

.Call("run_testthat_tests", PACKAGE = <pkgName>)

as necessary within your unit test suite.

See also

Catch, the library used to enable C++ unit testing.