Change fuzzing test to avoid leaving files around

[dmjb]

The previous implementation would create a test file but never clean it up, which causes problems when running the tests locally.

Summary

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Fixes #(related issue)

Change Type

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• Bug fix (resolves an issue without affecting existing features)
• Feature (adds new functionality without breaking changes)
• Breaking change (may impact existing functionalities or require documentation updates)
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Testing

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Review Checklist:

• Reviewed my own code for quality and clarity.
• Added comments to complex or tricky code sections.
• Updated any affected documentation.
• Included tests that validate the fix or feature.
• Checked that related changes are merged.

[dmjb]

FYI @AdamKorcz