r testthat and covr use in a non-package library

I'd like to be able to use testthat and covr in a project that is not an r package. In fact does not use any third party services. Just a collection of plain-old-r source files

I am struggling to find out if this is possible, and if so, the instructions on how to set this is up.

What I have found assumes you are writing an r package. I like to avoid this overhead.

Prior Art:

1. https://www.rstudio.com/resources/webinars/covr-bringing-test-coverage-to-r/
2. https://walczak.org/2017/06/how-to-add-code-coverage-codecov-to-your-r-package/

That should be possible without problems.

First: I have one file with code that should be tested named code.R:

f1 <- function(n, ...) {
    rnorm(n = n, ...)
}

Second: Then I have a file with tests named tests.R:

source("code.R")

test_that("Random tests", {
    tmp1 <- f1(10)
    expect_type(tmp1, "double")
    expect_equal(length(tmp1), 10)
})

Third: And then you can run tests as well as coverage like this:

library(testthat)
library(covr)

test_file("tests.R")

res <- file_coverage("code.R", "tests.R")
res
report(res)

Multiple files should be no problem.