Fix and re-add subscription test

[paologalligit]

Description

This PR reintroduce the pending subscription test previously deleted because flaky.

Fixes # issue-214

Type of change

• [x] Add new test

Checklist:

• [x] My code follows the style guidelines of this project
• [x] I have performed a self-review of my code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I have made corresponding changes to the documentation
• [x] My changes generate no new warnings
• [x] Any dependent changes have been merged and published in downstream modules
• [x] I have not added any vulnerable dependencies to my code

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 62.70%. Comparing base (27e60e6) to head (706858b).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #763 +/- ## ========================================== + Coverage 62.59% 62.70% +0.10% ========================================== Files 199 199 Lines 18093 18093 ========================================== + Hits 11326 11345 +19 + Misses 5685 5664 -21 - Partials 1082 1084 +2 ```

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