test: build inline css

[btea]

Description

Supplement #15554.

Additional context

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines, especially the Pull Request Guidelines.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Update the corresponding documentation if needed.
• Ideally, include relevant tests that fail without this PR but pass with it.

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[btea]

@patak-dev Hi, I tried to add a test, but an error occurred in ci. I don't know what to do next, I hope to get your guidance, thank you!

[patak-dev]

@btea it would be better to add this directly to the css playground so we avoid creating too many of them.

[sapphi-red]

Closing as it seems the tests added by #16421 covers #15554 as well. I reverted the change in #15554 and the test failed correctly.