if (requireNamespace("tinytest", quietly=TRUE)) {

  ## Set a seed to make the test deterministic
  set.seed(42)
  Sys.setenv("R_TESTS"="")

  ## there are several more granular ways to test files in a tinytest directory,
  ## see its package vignette; tests can also run once the package is installed
  ## using the same command `test_package(pkgName)`, or by director or file
  tinytest::test_package("interleave")
}