Summary

Users can now shard tests across CI machines and merge all results into a single report with rstest merge-reports, including combined coverage.

Background

When tests are split across multiple CI machines using --shard, each shard produces isolated test reports and coverage data with no way to combine them into a unified result.

Implementation

• Added a blob built-in reporter that serializes test results, durations, snapshots, console logs, and errors to JSON files (.rstest-reports/blob-{index}-{count}.json)
• Added rstest merge-reports [path] CLI command that loads blob files, replays results through configured reporters, merges coverage data via istanbul, and optionally cleans up with --cleanup
• Blob reporter is automatically excluded during merge to avoid re-producing blob output
• Per-shard duration breakdown is displayed during merge

Shard Workflow

1. Run each shard with the blob reporter to generate blob report files:

# On CI machine 1
npx rstest run --shard 1/3 --reporter=blob

# On CI machine 2
npx rstest run --shard 2/3 --reporter=blob

# On CI machine 3
npx rstest run --shard 3/3 --reporter=blob

2. Collect all .rstest-reports/ directories into a single location, then merge:

npx rstest merge-reports

By default, blob reports are read from .rstest-reports/ in the project root. You can specify a custom path:

npx rstest merge-reports ./custom-reports-dir

The merge command will:

• Combine test results from all shards
• Run configured reporters (e.g., default, junit) with the merged data
• Merge and generate coverage reports (if coverage is enabled)

Use --cleanup to remove the blob reports directory after merging:

npx rstest merge-reports --cleanup

Related Links

close #1044

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).