Disable test count check for shards

[Fox32]

I'm running with sharding in a package that has less tests than shards. We have a mono repo that have multiple packages and we want to use sharding with the same configuration across all of them. But some of our packages are very small and don't reach the amount of shards.

For example, if I run with --shard 2/2 in a package with a single test, I get the error Error: --shard <count> must be a smaller than count of test files. Resolved 1 test files for --shard=2/2..

I actually don't care that the second shard is empty if the first one isn't. I know there is a --passWithNoTests flag to not fail if not tests are there, but this seems to be evaluated globally and not per shard. Is there something similar flag for sharding?

[ArianMakiabadi]

well there’s no flag for this right now.

The error happens before Vitest even gets to the “no tests” logic. sharding fails early if the shard count is larger than the number of resolved test files. So --passWithNoTests can’t help here since it’s global and only applies when zero tests are found, not when the shard config itself is considered invalid.

We’ve hit the same thing in a monorepo. The only real workaround today is to handle it outside Vitest, e.g.:

• detect how many test files a package has
• if it’s fewer than the shard count, don’t pass --shard at all (or clamp the shard count)
• otherwise run with the normal i/n shard config

It’s a bit annoying, but doing it in the CI matrix is usually the least painful option.

What you’re describing (allowing empty shards or a --passWithNoTestsPerShard / --allowEmptyShards type option) sounds reasonable to me and feels more like a missing feature than misuse. Especially in monorepos where you want one shard config everywhere.

So yeah; I don’t think you’re missing anything. This is probably worth a feature request.