How to initialize database dependency for unit tests

[mplorentz]

I'm having trouble with what I think should be a simple task for a dependency injection library. I feel like I am missing something.

My app uses Core Data and I have created a PersistenceController class that sets up the Core Data stack and manages various NSManagedObjectContexts. This persistence controller is managed by the Dependencies library and I have configured a testValue that uses an in-memory persistent store.

How can I create a fresh PersistenceController dependency for each test in an XCTestCase subclass?

I know I could wrap every test in a withDependencies(:operation:) block, but that's a lot of duplicated code, so I'm looking for a cleaner way. I tried abusing withEscapedDependencies() to set up a new PersistenceController in setUp() and not yield the continuation until tearDown() but that didn't seem to work either.

[mbrandonw]

Hi @mplorentz, I'm not super familiar with the specifics of CoreData anymore, but there's no need to use withDependencies in each individual test method. You can do it once for all tests in a class by overriding invokeTest. We have some docs here:

swift-dependencies/Sources/Dependencies/Documentation.docc/Articles/OverridingDependencies.md

Lines 127 to 134 in b323c53

	Sometimes there is a dependency that you want to override in a particular way for the entire test
	case. For example, your feature may make extensive use of the ``DependencyValues/date`` dependency
	and it may be cumbersome to override it in every test. Instead, it can be done a single time by
	overriding `invokeTest` in your test case class:
	```swift
	final class FeatureTests: XCTestCase {
	override func invokeTest() {

[mplorentz]

Thank you so much! This is exactly what I needed. I skimmed that docs page several times and somehow didn't see that part 😬.

[acosmicflamingo]

Geez...how did I miss that? 🤩