fix:(tests): convert testCases type to map[string]struct

[abelhoula]

What this PR does / why we need it:

Types of changes

• [x] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] CVE Report (Scanner found CVE and adding report)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Documentation only

Which issue/s this PR fixes

How Has This Been Tested?

Checklist:

• [x] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] I've read the CONTRIBUTION guide
• [x] All new and existing tests passed.

Does my pull request need a release note?

Any user-visible or operator-visible change qualifies for a release note. This could be a:

• CLI change
• API change
• UI change
• configuration schema change
• behavioral change
• change in non-functional attributes such as efficiency or availability, availability of a new platform
• a warning about a deprecation
• fix of a previous Known Issue
• fix of a vulnerability (CVE)

No release notes are required for changes to the following:

• Tests
• Build infrastructure
• Fixes for unreleased bugs

For more tips on writing good release notes, check out the Release Notes Handbook

PLACE RELEASE NOTES HERE

[abelhoula]

Related to https://github.com/edixos/Nauticus/issues/49

[github-actions[bot]]

This is stale, but we won't close it automatically, just bare in mind the maintainers may be busy with other tasks and will reach your issue ASAP. If you have any question or request to prioritize this, please reach #nautius on Kubernetes Slack.