New Core Data Stack (PersistenceController) in Unit Tests

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Created Sep ’20

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With the new Swift App Xcode template, I see the PersistenceController struct was added with a shared and preview instance to serve as the Core Data stack. From what I understand, the preview instance is for SwiftUI previews.

If I have a service class that takes an instance of my Core Data stack, should I be using the preview instance as part of my unit tests? Or should I create some sort of spy/fake to pass into the service class I am testing?

In general, what is the best practices for testing classes that use Core Data?

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Answer 1

malc OP

Sep ’20

Testing units together is called integration testing. Just add another instance to the PersistenceController that uses an in-memory store the same as the preview instance. You can make methods to add sample data and call them depending on what you would like in each.

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