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## Summary
Put together a technique to reuse previews to generate and assert
snapshots.
This either saves time writing snapshot tests or makes snapshot tests
more useful by using them as previews.
This is implemented in a couple of libraries already
([example](https://github.com/BarredEwe/Prefire)). Went with a simple
implementation here but a library can be adopted to leverage additional
features and support.
To hold the code for snapshotting, a new framework was introduced,
SharedTesting, to collect all the utilities built for testing. It must
only be imported in test targets.
The preview side of the code lives in the Shared framework.
Applying this new technique will come in a separate PR.
[Original PR](https://github.com/home-assistant/iOS/pull/3484)
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Co-authored-by: Bruno Pantaleão Gonçalves <5808343+bgoncal@users.noreply.github.com>
