Adopt StateStoreViewModelV2 in the authentication screens and some settings screens. (#4083)

* Add some tests for DeferredFulfillment with Observation.

* Use StateStoreViewModelV2 in AuthenticationStartScreen.

* Use StateStoreViewModelV2 in ServerConfirmationScreen.

* Use StateStoreViewModelV2 in ServerSelectionScreen.

* Use StateStoreViewModelV2 in SoftLogoutScreen.

* Use StateStoreViewModelV2 in SettingsScreen.

* Use StateStoreViewModelV2 in DeveloperOptionsScreen.

* Use StateStoreViewModelV2 in AdvancedSettingsScreen.

UnitTests/Sources/DeferredFulfillmentTests.swift

@@ -0,0 +1,81 @@
+//
+// Copyright 2025 New Vector Ltd.
+//
+// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+// Please see LICENSE files in the repository root for full details.
+//
+
+@testable import ElementX
+import XCTest
+
+class DeferredFulfillmentTests: XCTestCase {
+    private let observable = SomeObservable()
+    
+    func testObservableWithoutUpdate() async throws {
+        // Given a deferred fulfilment on a value that already matches the expected value.
+        let initialValue = observable.counter
+        let deferred = deferFulfillment(observable.observe(\.counter)) { $0 == initialValue }
+        
+        // Then the test should be fulfilled by the initial value and shouldn't timeout whilst waiting for a update.
+        try await deferred.fulfill()
+    }
+    
+    func testObservableWithSynchronousUpdate() async throws {
+        // Given a deferred fulfilment for an expected value.
+        let newValue = 100
+        let deferred = deferFulfillment(observable.observe(\.counter)) { $0 == newValue }
+        
+        // When that value is changed synchronously.
+        observable.counter = newValue
+        XCTAssertEqual(observable.counter, newValue)
+        
+        // Then the test should be fulfilled.
+        try await deferred.fulfill()
+        XCTAssertEqual(observable.counter, newValue)
+    }
+    
+    func testObservableAsynchronousUpdate() async throws {
+        // Given a deferred fulfilment for an expected value.
+        let newValue = 100
+        let deferred = deferFulfillment(observable.observe(\.counter)) { $0 == newValue }
+        
+        // When that value is changed asynchronously.
+        Task { try await observable.setCounter(newValue, delay: .seconds(1)) }
+        XCTAssertEqual(observable.counter, 0)
+        
+        // Then the test should be fulfilled once the update has taken place.
+        try await deferred.fulfill()
+        XCTAssertEqual(observable.counter, newValue)
+    }
+    
+    func testObservableMultipleUpdates() async throws {
+        // Given a deferred fulfilment for an expected value.
+        let finalValue = 500
+        let deferred = deferFulfillment(observable.observe(\.counter)) { $0 == finalValue }
+        
+        // When that value is changed asynchronously with some intermediate values before it is reached.
+        Task {
+            try await observable.setCounter(100, delay: .seconds(.random(in: 1.0...2.0)))
+            try await observable.setCounter(250, delay: .seconds(.random(in: 1.0...2.0)))
+            try await observable.setCounter(finalValue, delay: .seconds(.random(in: 1.0...2.0)))
+        }
+        XCTAssertEqual(observable.counter, 0)
+        
+        // Then the test should be fulfilled once the expected update has taken place.
+        try await deferred.fulfill()
+        XCTAssertEqual(observable.counter, finalValue)
+    }
+}
+
+// MARK: - Helpers
+
+@Observable private class SomeObservable {
+    var counter = 0
+    
+    func setCounter(_ newValue: Int, delay: Duration? = nil) async throws {
+        if let delay {
+            try await Task.sleep(for: delay)
+        }
+        counter = newValue
+    }
+}

UnitTests/Sources/ServerConfirmationScreenViewModelTests.swift

@@ -150,7 +150,7 @@ class ServerConfirmationScreenViewModelTests: XCTestCase {
         XCTAssertNil(context.alertInfo)
         
         // When continuing from the confirmation screen.
-        let deferred = deferFulfillment(context.$viewState) { $0.bindings.alertInfo != nil }
+        let deferred = deferFulfillment(context.observe(\.alertInfo)) { $0 != nil }
         context.send(viewAction: .confirm)
         try await deferred.fulfill()
         
@@ -167,7 +167,7 @@ class ServerConfirmationScreenViewModelTests: XCTestCase {
         XCTAssertNil(context.alertInfo)
         
         // When continuing from the confirmation screen.
-        let deferred = deferFulfillment(context.$viewState) { $0.bindings.alertInfo != nil }
+        let deferred = deferFulfillment(context.observe(\.alertInfo)) { $0 != nil }
         context.send(viewAction: .confirm)
         try await deferred.fulfill()
         

UnitTests/Sources/ServerSelectionScreenViewModelTests.swift

@@ -43,7 +43,7 @@ class ServerSelectionScreenViewModelTests: XCTestCase {
         
         // When selecting a server that doesn't support login.
         context.homeserverAddress = "server.net"
-        let deferred = deferFulfillment(context.$viewState) { $0.bindings.alertInfo != nil }
+        let deferred = deferFulfillment(context.observe(\.alertInfo)) { $0 != nil }
         context.send(viewAction: .confirm)
         try await deferred.fulfill()
         
@@ -78,7 +78,7 @@ class ServerSelectionScreenViewModelTests: XCTestCase {
         
         // When selecting a server that doesn't support registration.
         context.homeserverAddress = "example.com"
-        let deferred = deferFulfillment(context.$viewState) { $0.bindings.alertInfo != nil }
+        let deferred = deferFulfillment(context.observe(\.alertInfo)) { $0 != nil }
         context.send(viewAction: .confirm)
         try await deferred.fulfill()
         
@@ -96,7 +96,7 @@ class ServerSelectionScreenViewModelTests: XCTestCase {
                        "The standard footer message should be shown.")
         
         // When attempting to discover an invalid server
-        var deferred = deferFulfillment(context.$viewState) { $0.isShowingFooterError }
+        var deferred = deferFulfillment(context.observe(\.viewState.isShowingFooterError)) { $0 }
         context.homeserverAddress = "idontexist"
         context.send(viewAction: .confirm)
         try await deferred.fulfill()
@@ -108,7 +108,7 @@ class ServerSelectionScreenViewModelTests: XCTestCase {
                           "The error message should be shown.")
         
         // And when clearing the error.
-        deferred = deferFulfillment(context.$viewState) { !$0.isShowingFooterError }
+        deferred = deferFulfillment(context.observe(\.viewState.isShowingFooterError)) { !$0 }
         context.homeserverAddress = ""
         context.send(viewAction: .clearFooterError)
         try await deferred.fulfill()

UnitTests/Sources/SettingsScreenViewModelTests.swift

@@ -26,47 +26,20 @@ class SettingsScreenViewModelTests: XCTestCase {
     }
 
     @MainActor func testLogout() async throws {
-        var correctResult = false
-        
-        viewModel.actions
-            .sink { action in
-                switch action {
-                case .logout:
-                    correctResult = true
-                default:
-                    break
-                }
-            }
-            .store(in: &cancellables)
-
+        let deferred = deferFulfillment(viewModel.actions) { $0 == .logout }
         context.send(viewAction: .logout)
-        await Task.yield()
-        XCTAssert(correctResult)
+        try await deferred.fulfill()
     }
 
     func testReportBug() async throws {
-        var correctResult = false
-        viewModel.actions
-            .sink { action in
-                correctResult = action == .reportBug
-            }
-            .store(in: &cancellables)
-        
+        let deferred = deferFulfillment(viewModel.actions) { $0 == .reportBug }
         context.send(viewAction: .reportBug)
-        await Task.yield()
-        XCTAssert(correctResult)
+        try await deferred.fulfill()
     }
     
     func testAnalytics() async throws {
-        var correctResult = false
-        viewModel.actions
-            .sink { action in
-                correctResult = action == .analytics
-            }
-            .store(in: &cancellables)
-        
+        let deferred = deferFulfillment(viewModel.actions) { $0 == .analytics }
         context.send(viewAction: .analytics)
-        await Task.yield()
-        XCTAssert(correctResult)
+        try await deferred.fulfill()
     }
 }

UnitTests/Sources/SoftLogoutScreenViewModelTests.swift

@@ -10,7 +10,7 @@ import XCTest
 @testable import ElementX
 
 @MainActor
-class SoftLogoutViewModelTests: XCTestCase {
+class SoftLogoutScreenViewModelTests: XCTestCase {
     let credentials = SoftLogoutScreenCredentials(userID: "mock_user_id",
                                                   homeserverName: "https://example.com",
                                                   userDisplayName: "mock_username",