ESLint Tests

Write rule tests with RuleTester and run them under vitest.

At a high level:

• If the repo already has an ESLint rule and test layout, follow that structure.
• If the repo does not have an ESLint rule and test layout yet, default to eslint/custom-rules for rules and eslint/tests for rule tests.
• Mirror each custom rule with a matching test file in the location the repo uses for ESLint rule tests.
• Keep the tests focused on the rule contract, not unrelated parser or config behavior.
• Prefer small inline code samples that make the valid or invalid case obvious.

Use this structure for each custom rule:

• 10 valid examples that should produce no errors.
• 10 invalid examples that should report the expected rule message(s).

Guidelines: