[Bug]: Issue with Slashes (`/`) in File Names When Using the `--shard` Option

[hiraly]

To Reproduce

When running the Storybook Test Runner with the --shard option in GitHub Actions, issues occur due to the inclusion of slashes (e.g., 1/10) in shard names. This is particularly problematic when renaming files or uploading artifacts.

Steps to reproduce:

1. Execute the following GitHub Actions job:

   jobs:
     storybook-test:
       strategy:
         matrix:
           shard: [1/10, 2/10]
       steps:
         - name: Run Storybook Tests
           run: npx storybook test --shard=${{ matrix.shard }} --coverage
         - name: Upload Coverage File
           run: mv coverage/storybook/coverage.json coverage/storybook/coverage-${{ matrix.shard }}.json

2. The job fails with an error because file names containing slashes (e.g., coverage-1/10.json) are invalid:

   mv: cannot move 'coverage/storybook/coverage.json' to 'coverage/storybook/coverage-1/10.json': No such file or directory
   

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System

Its on Github Action CI

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Additional Context

In GitHub Actions, file and artifact names containing slashes (/) are invalid and result in errors. Currently, we use the following workaround:

1. Escape shard names (e.g., 1/10) using a custom script:

   mv coverage/storybook/coverage.json coverage/storybook/coverage-1_10.json

2. Use the escaped shard names (e.g., 1_10) as artifact names.

To improve usability, we propose the following enhancements:

• Add internal logic to escape slashes in shard names.
• Alternatively, provide an option to customize the shard name format.

These changes would eliminate the need for manual scripting and make the Test Runner more CI-friendly.