Running @testitem in VS Code fails

Hi everyone,
I am currently developing a small package and wrote some Unit-tests for it. Since I am developing it in VS Code, I am using the TestItemRunner.jl package.
The tests also work as expected when using the Package mode in the REPL and executing test PackageName.
Yet when using the VS Code UI to execute a test set, I only receive the error “Unable to identify a Julia package for this test item.” and the only place where I found this error was as part of the source code of Julia VS Code extension (, line 330), yet I was unable to understand what causes this error.
Is there a common mistake that causes this error?

Kind regards,

Maybe relevant info:
I am using the “new” way of specifying test-specific dependencies (i.e. with an additional test/Project.toml file), but have also tested the “old” way and it has not changed anything.

Is your directory PackageName or PackageName.jl? I think there’s still a bug in the extension where it only works for the former name (without jl).

The folder was indeed named PackageName.jl before but renaming it did not change anything, but still, thank you!

Then don’t know… But the testrunner definitely works with test/Project.toml.

Do you maybe have a public package on top of your mind that has such a setup? Maybe I can find the causing difference to my setup.

This is a small package that uses it: GitHub - m3g/ChunkSplitters.jl: Simple chunk splitters for parallel loop executions

I use test/Project.toml in all my packages, and also use @testitems in many of them. A basic example is Alexander Plavin / Skipper.jl · GitLab.

Thanks to both of you, after having tested some more stuff out, I finally figured out, that it was because I was missing the version field in the base Project.toml file.