Refactor backend tests

[PardhavMaradani]

Changes made in this Pull Request:

• Refactor backend tests to keep the widgets runs independent and simple

PR Checklist

• Tests?
• Docs?
• CHANGELOG updated?
• Issue raised/referenced?

[read-the-docs-community]

Documentation build overview

📚 mdadash | 🛠️ Build #33333258 | 📁 Comparing db9b26d against latest (524bd29)

  🔍 Preview build  

3 files changed

± autosummary/mdadash.backend.kernel.core.html
± _modules/mdadash/backend/kernel/core.html
± _modules/mdadash/backend/widgets/base.html

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (524bd29) to head (db9b26d).

Additional details and impacted files

Components	Coverage Δ
frontend	100.00% <ø> (ø)
backend	100.00% <100.00%> (ø)

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