How to test usage of notificationCenter

[martin-muller]

Hi all,

I'm wondering what's the best approach to test that my client has sent a notification.

struct BestClient {
    let doImportantWork: () async throws -> Void
}

extension BestClient {
    static let live = {
        @Dependency(\.notificationCenter) var notificationCenter
        
        return BestClient(
            doImportantWork: {
                // ...
                
                notificationCenter.post(name: .init("important"))
            }
        )
    }()
}

My initial instinct was to override the notificationCenter dependency using withDependencies and either create a whole new NotificationCenter.Dependency or override just the post and assert that the call was made, but the init is internal and the funcs are internal lets. Then I thought I can import DependenciesAdditions as testable and have the init available, but weirdly enough that didn't work, maybe something in our setup.

Im aware there is public init that takes NotificationCenter, but since we already have the wrapper client object NotificationCenter.Dependency, it seems like unnecessary complication to use the Foundation's NotificationCenter for testing.

Thank you for the wonderful library!

[tgrapperon]

Hey @martin-muller! The initial variant of NotificationCenter had a custom value that allowed some level of observation/introspection, but it was using a protocol, and I got rid of it after some time to simplify the API. I'll check if this is still easily achievable given the API that finally shipped!