Resolves#45220 (one of many small PRs, we are close)
## Testing
- [X] QA'd all new/changed functionality manually
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## Summary by CodeRabbit
* **Tests**
* Refactored test infrastructure for scheduling components to use
centralized test utilities.
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**Note:** This release contains no user-facing changes. All
modifications are internal testing and code organization improvements.
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[](https://app.coderabbit.ai/change-stack/fleetdm/fleet/pull/45609)
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