Refactor cache busting middleware tests to conform to test standards

[coderabbitai]

Context

The cache busting middleware functionality is working as expected and can be merged, but the tests need to be refactored to conform to the project's test standards.

Issues identified

1. Test naming/phrasing: Tests need to use correct Given-When-Then format. Currently, parts of the Given are in the When section and parts of the When are in the Then section.

2. Test organization: Tests are validating multiple separate concerns in single test cases:

   • cacheBustingConfig functionality
   • Interaction with handlers

   These should be split into different tests and probably different files.

3. Additional modifications: Other modifications suggested by Kasper should also be applied.

Related PR and Discussion

• PR: feat: Adds support for cache busting #192
• Discussion: feat: Adds support for cache busting #192 (comment)

Note

The interface probably will not change, so this refactoring is focused on test organization and conformance to standards.

Requested by: @SandPod