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devtools::test_coverage_active_file() and devtools::test() disagree on the error message to snapshot #2698
Closed as not planned
Description
Repo with reprex: https://github.com/etiennebacher/bug.testthat.coverage (tested in Positron and RStudio)
> packageVersion("covr")
[1] ‘3.6.5.9001’
> packageVersion("devtools")
[1] ‘2.5.2.9000’
> packageVersion("testthat")
[1] ‘3.3.2.9000’Setup:
-
R/foo.R:f <- function(x) { if (x) {} }
-
tests/testthat/test-foo.R:test_that("foo", { expect_snapshot(f(x = logical(0)), error = TRUE) })
-
tests/testthat/_snaps/foo.md:# foo Code f(x = logical(0)) Condition Error in `if (x) ...`: ! argument is of length zero
Bug:
- Open
tests/testthat/test-foo.Rin your editor (so that it is detected as the "active file") devtools::test()reports no issuedevtools::test_coverage_active_file()is not happy with the snapshot:
> devtools::test_coverage_active_file()
── Failure: foo ──────────────────────────────────────────────────────────────────────────────────────────
Snapshot of code has changed:
old | new
[1] Code | Code [1]
[2] f(x = logical(0)) | f(x = logical(0)) [2]
[3] Condition | Condition [3]
[4] Error in `if (x) ...`: - Error in `if (...) NULL`: [4]
[5] ! argument is of length zero | ! argument is of length zero [5]
* Run testthat::snapshot_accept("foo") to accept the change.
* Run testthat::snapshot_review("foo") to review the change.
Error:
! Test failed with 1 failure and 0 successes.
Activity
etiennebacher commentedon Jun 23, 2026
This is related to how
covrworks. Hopefully this helps someone.Why do snapshot messages change?
When
covrruns, it doesn't run tests right away but it instruments the functions in the package first. This means that it inserts pieces of code to count the number of times a line of code is run during the tests. For instance, this piece of code:would become this:
Therefore, when
xhas length 0 then the error:becomes:
because the
...represents the block:These are the two different messages that we see in the snapshots.