CoreData test utilities?

[jeremy-w]

Are there any blobs of code we frequently rewrite as part of testing something that relies on Core Data? If so, could we make those available for use in tests alongside the useful methods available for getting Core Data set up in the main app?

[lyricsboy]

The most reusable thing I frequently appreciate is the ability to create stack backed by an in-memory persistent store. So, for example, in an app I have an initializer like:

typedef NS_ENUM(NSUInteger, PSICoreDataStackStoreType) {
    PSICoreDataStackStoreTypeInMemory,
    PSICoreDataStackStoreTypeOnDisk,
};

...

- (instancetype)initWithStoreType:(PSICoreDataStackStoreType)storeType;

And then when I'm adding the persistent store, I switch on storeType as appropriate.

Having the stack use a scratch store makes it really easy to run tests in isolation.

[rcedwards]

I'd really like to add some examples of unit testing a model version migration also.