Feat/929 tests improve notification showcase

[nikolay-vasilev-prime]

Overview

Closes: #929

Checklist

Implementation

• Implementation matches ticket acceptance criteria and technical notes
• Manually tested against Acceptance Criteria
• UI checked in Light / Dark mode

Stability

• Checked if changes affect any features and verified affected features work as expected
• Added unit tests for new code and verified existing tests work as expected

Code quality

• Updated CHANGELOG.md, README.md and package versions in pubspec.yaml
• Dependencies are updated to latest versions or new tickets are created if there are breaking changes or deprecations
• If an unrelated part of the codebase needs to be updated or refactored, create tickets with proposed changes

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.66%. Comparing base (f3e0d8a) to head (aca14ae).
Report is 19 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #993   +/-   ##
========================================
  Coverage    95.66%   95.66%           
========================================
  Files          121      121           
  Lines         2632     2632           
========================================
  Hits          2518     2518           
  Misses         114      114           

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