test: improve merge reports test

[antazoey]

What I did

I was having some issues and was not 100% convinced it wasn't coming from evm-trace so I improved the test to make me convinced.

How I did it

Make test more complicated and transparent of what is happening

How to verify it

Checklist

• [ ] Passes all linting checks (pre-commit and CI jobs)
• [ ] New test cases have been added and are passing
• [ ] Documentation has been updated
• [ ] PR title follows Conventional Commit standard (will be automatically included in the changelog)