Is there a possibility to set a different Sys.getenv("R_CONFIG_ACTIVE") value when run in tests using testthat?

For example, my config.yml might look like this:

default:
  db: "my-prod.db"
test:
  db: "my-test.db"

When I run config::get("db") from a non-test environment I want to get my-prod.db but when I use testthat::test_dir() or devtools::test() or shiny::runTests() I want to get my-test.db.

I would be able to influence this by setting Sys.setenv("R_CONFIG_ACTIVE" = "test").