StoreKit testing in Swift
The second iteration of the StoreKit framework was the most significant change in my apps during the last few years. The recent version of the StoreKit framework has fully adopted Swift language features like async and await. This week, we will talk about the StoreKitTest framework, which is not a part of StoreKit 2 but is tightly coupled with it.
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The StoreKitTest framework allows us to write tests for in-app product purchasing, refunding, and restoring features. You can cover almost every aspect of the in-app purchase with tests using the StoreKitTest framework. Before starting, you should create a StoreKit Configuration File.
To learn more about the basics of the StoreKit 2, take a look at my “Mastering StoreKit 2” post.
The StoreKitTest framework provides us with the SKTestSession type. Using an instance of the SKTestSession type, we can purchase in-app products, manage transactions, refund and expire subscriptions, etc.
Let’s start by creating a test case for our StoreKit-related features. I usually have a type called SettingsStore, which defines user configuration and handles in-app purchases. We will cover the in-app purchase management part of the SettingsStore with tests by using the StoreKitTest framework.
@MainActor final class StoreKitTests: XCTestCase {
func testProductPurchase() async throws {
let session = try SKTestSession(configurationFileNamed: "SugarBot Food Calorie Counter")
session.disableDialogs = true
session.clearTransactions()
}
}
As you can see in the example above, we initialize an instance of the SKTestSession type. Then, we call the clearTransactions function to remove all the transactions we may have stored from the previous launches. We also turn off dialogs to automate the purchase confirmation flow easily.
Now, we can use our SettingsStore type to purchase products and process subscription status. The SKTestSession type also allows us to buy a product that simulates the purchase outside the app. For example, it might be a purchased product with family sharing enabled.
@MainActor final class StoreKitTests: XCTestCase {
var store: SettingsStore!
override func setUp() {
store = SettingsStore()
}
func testProductPurchase() async throws {
let session = try SKTestSession(configurationFileNamed: "SugarBot Food Calorie Counter")
session.disableDialogs = true
session.clearTransactions()
try await session.buyProduct(identifier: "annual")
guard let product = try await Product.products(for: ["annual"]).first else {
return XCTFail("Can't load products...")
}
let status = try await product.subscription?.status ?? []
await store.processSubscriptionStatus(status)
XCTAssertFalse(store.activeSubscriptions.isEmpty)
}
}
As you can see in the example above, we use the buyProduct function on an instance of the SKTestSession type to simulate a purchase. We can also use the expireSubscription function of the SKTestSession type to expire ongoing subscriptions and verify how our app processes this data.
@MainActor final class StoreKitTests: XCTestCase {
var store: SettingsStore!
override func setUp() {
store = SettingsStore()
}
func testExpiredProduct() async throws {
let session = try SKTestSession(configurationFileNamed: "SugarBot Food Calorie Counter")
session.disableDialogs = true
session.clearTransactions()
let transaction = try await session.buyProduct(identifier: "annual")
let activeProducts = try await Product.products(for: ["annual"])
let activeStatus = try await activeProducts.first?.subscription?.status ?? []
await store.processSubscriptionStatus(activeStatus)
XCTAssertFalse(store.activeSubscriptions.isEmpty)
try session.expireSubscription(productIdentifier: "annual")
let expiredProducts = try await Product.products(for: ["annual"])
let expiredStatus = try await expiredProducts.first?.subscription?.status ?? []
await store.processSubscriptionStatus(expiredStatus)
XCTAssertTrue(store.activeSubscriptions.isEmpty)
}
}
The SKTestSession type also allows us to simulate product refunds using the refundTransaction function. Another exciting option is to test how the app reacts to transaction updates.
let transaction = try await session.buyProduct(identifier: "annual")
// verify purchase ...
try session.refundTransaction(identifier: UInt(transaction.id))
// verify refund ...
You can also use the askToBuyEnabled property to enable the ask-to-buy feature and then use the approveAskToBuyTransaction or declineAskToBuyTransaction functions to approve or decline purchases. In this case, the transaction should change from pending to successful.
session.askToBuyEnabled = true
await store.purchase("annual")
// verify purchase ...
let declined = store.pendingTrancations.first?.id ?? 0
try session.declineAskToBuyTransaction(identifier: UInt(declined.id))
// verify purchase ...
await store.purchase("annual")
// verify purchase ...
let approved = store.pendingTrancations.first?.id ?? 0
try session.approveAskToBuyTransaction(identifier: UInt(approved.id))
// verify purchase ...
As you can see in the example above, we use an instance of the SKTestSession type to simulate ask-to-buy and verify the behavior of our app while the purchase is approved or declined.
This week, we learned how to use the StoreKitTest framework to verify how our app handles in-app purchases and user flows like refunds, ask-to-buy, and subscription expiration. I hope you enjoy the post. Feel free to follow me on Twitter and ask your questions related to this post. Thanks for reading, and see you next week!