Code coverage test fails on Windows while it works on Mac OS X

[schaffstein]

I am struggling with a code coverage test (using covr 3.4.0) on a windows machine (Windows 10 Enterprise; R 3.6.2). To verify the behaviour I wrote a very basic package with just one hello() function and a testthat-test covering exactly this function. I run the test with the following code:

library(covr)
cov <- covr::package_coverage(quiet = FALSE, clean = FALSE)

On the windows machine it returns the following error:

Running specific tests for package ‘dummyTestthat’
  Running ‘testthat.R’
Warnmeldung:
In structure(c(coverage, res), class = "coverage", package = pkg,  :
  Calling 'structure(NULL, *)' is deprecated, as NULL cannot have attributes.
  Consider 'structure(list(), *)' instead.

Running the exact same script on my Mac OS X machine (R 3.6.2) works nicely and returns a test coverage value of 100% (which is correct).

Do you have any idea what's failing on the windows machine? (If it helps, I'll happily supply you with my dummy package.)

[jimhester]

I think likely it is failing before this warning, but don't have enough information here to determine exactly why.

[schaffstein]

Which information can I supply to help you identify the problem? I'd be happy to give you all the details...

[jimhester]

You would likely need to provide an example package that exhibits this behavior for me to reproduce it.