Testthat snapshots not uploading

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Describe the bug

I'm using these settings in my yaml, hoping to upload my testthat snapshot files to a GitHub artifact:

      - uses: r-lib/actions/check-r-package@v2
        with:
          upload-snapshots: true
          build_args: 'c("--no-manual","--compact-vignettes=gs+qpdf")'

But these get uploaded instead of the snapshots:

Finished uploading artifact content to blob storage!
SHA256 hash of uploaded artifact zip is 4a1a325c91fd09fc5bbf23aa49711abc2984151c64dc5ad1364b762b6957536a
Finalizing artifact upload
Artifact Linux-X64-rrelease-3-results.zip successfully finalized. Artifact ID 1643076474
Artifact Linux-X64-rrelease-3-results has been successfully uploaded! Final size is 2408648 bytes. Artifact ID is 1643076474

To Reproduce

https://github.com/FredHutch/VISCtemplates/actions/runs/9690680996/job/26740916919 https://github.com/FredHutch/VISCtemplates/pull/168

Expected behavior

I expected the testthat snapshots to get uploaded to a GHA artifact.

Additional context

There are no original comparison snapshots, i.e. the snapshots are being created from scratch. The _snaps folder is .gitignored and .Rbuildignored. The R CMD check and test results are the same locally and on GHA.