Have you tried adding session.resetToDefaultState() to the setupError? override func setUpWithError() throws { session = try SKTestSession(configurationFileNamed: "Configuration") session.resetToDefaultState() session.clearTransactions() session.disableDialogs = true } However, in some cases (like mine), you may need to add this line for each test block. I don't know if this issue is caused by my logic or a bug in StoreKitTest. override func setUpWithError() throws { session = try SKTestSession(configurationFileNamed: "Configuration") // Even if I add this in setUpWithError, a test will always return an unexpected error. session.resetToDefaultState() session.clearTransactions() session.disableDialogs = true } func testExample() async throws { // you'd need to insert this here but it depends on your code session.resetToDefaultState() session.clearTransactions() session.disableDialogs = true let products = try await Product.products(for: [productID]) let value = try await products[0].purchase() switch value { case .success(let verificationResult): switch verificationResult { case .verified(let signedType): XCTAssertEqual(signedType.productID, productID) case .unverified: XCTFail() } case .userCancelled, .pending: XCTFail() @unknown default: XCTFail() } } The WWDC2023 session mentioned using setSimulatedError(nil) to disable the previous setting, but currently, only setting nil didn't work, as far as I know. Refer to: WWDC2023 Session Additionally, once you set an error with setSimulatedError, a unit test always returns the error that you set previously (Configuration, as SKSession is shared).