Enable parallel UI test execution via per-session data isolation

Each test class now gets a unique session ID (UUID) passed to the app
via UI_TEST_SESSION_ID environment variable. The app uses this to:

- Route GroupUserDefaults to a session-specific UserDefaults suite,
  preventing tests from clobbering each other's AppStorage state
- Create an in-memory SwiftData container instead of the shared
  on-disk App Group store, eliminating SQLite contention

Refactored 8 test classes that bypassed BaseUITestCase.setUp() with
custom launch args — they now use overridable `localeArguments` and
`extraLaunchArguments` properties, keeping session ID injection
centralized. Added `relaunchApp(resetState:bypassSubscription:)` to
BaseUITestCase for tests that need mid-test relaunch with different
subscription state.

Includes a ParallelUITests.xctestplan with class-level parallelism
enabled and random execution ordering.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Reflect.xcodeproj/xcshareddata/xcschemes/ParallelUITests.xctestplan

@@ -0,0 +1,26 @@
+{
+  "configurations" : [
+    {
+      "id" : "9A1B2C3D-4E5F-6A7B-8C9D-0E1F2A3B4C5D",
+      "name" : "Parallel UI Tests",
+      "options" : {
+        "testExecutionOrdering" : "random"
+      }
+    }
+  ],
+  "defaultOptions" : {
+    "maximumTestExecutionTimeAllowance" : 180,
+    "testTimeoutsEnabled" : true
+  },
+  "testTargets" : [
+    {
+      "parallelizable" : true,
+      "target" : {
+        "containerPath" : "container:Reflect.xcodeproj",
+        "identifier" : "Tests iOS",
+        "name" : "Tests iOS"
+      }
+    }
+  ],
+  "version" : 1
+}

Shared/Persisence/SharedModelContainer.swift

@@ -36,6 +36,15 @@ enum SharedModelContainer {
     /// - Returns: Configured ModelContainer
     /// - Throws: SharedModelContainerError if creation fails
     static func create(useCloudKit: Bool = true) throws -> ModelContainer {
+        // When UI testing, use in-memory storage for parallel test isolation.
+        // Each test process gets its own empty container — no shared on-disk state.
+        // Check ProcessInfo directly to avoid depending on UITestMode (not in widget targets).
+        if ProcessInfo.processInfo.arguments.contains("--ui-testing") {
+            let schema = Schema([MoodEntryModel.self])
+            let config = ModelConfiguration(schema: schema, isStoredInMemoryOnly: true, cloudKitDatabase: .none)
+            return try ModelContainer(for: schema, configurations: [config])
+        }
+
         let schema = Schema([MoodEntryModel.self])
         let storeURL = try Self.storeURL
 

Shared/Random.swift

@@ -25,7 +25,26 @@ struct Constants {
 }
 
 struct GroupUserDefaults {
+    /// Whether the current process is a UI test session with an isolation ID.
+    /// Inlined from ProcessInfo to avoid depending on UITestMode (which isn't in widget targets).
+    private static var uiTestSessionID: String? {
+        guard ProcessInfo.processInfo.arguments.contains("--ui-testing") else { return nil }
+        return ProcessInfo.processInfo.environment["UI_TEST_SESSION_ID"]
+    }
+
+    /// The suite name currently in use. Used by resetAppState() to clear the correct domain.
+    static var currentSuiteName: String {
+        if let sessionID = uiTestSessionID {
+            return "uitest.\(sessionID)"
+        }
+        return Constants.currentGroupShareId
+    }
+
     static var groupDefaults: UserDefaults {
+        // When UI testing with a session ID, use a per-session suite for parallel isolation.
+        if let sessionID = uiTestSessionID {
+            return UserDefaults(suiteName: "uitest.\(sessionID)") ?? .standard
+        }
 #if DEBUG
         return UserDefaults(suiteName: Constants.groupShareIdDebug) ?? .standard
 #else

Shared/UITestMode.swift

@@ -42,6 +42,12 @@ enum UITestMode {
         ProcessInfo.processInfo.arguments.contains("--expire-trial")
     }
 
+    /// Unique session ID for parallel test isolation.
+    /// Each test class gets its own session, ensuring no shared state between parallel test runners.
+    static var sessionID: String? {
+        ProcessInfo.processInfo.environment["UI_TEST_SESSION_ID"]
+    }
+
     /// Seed fixture name if provided (via environment variable)
     static var seedFixture: String? {
         ProcessInfo.processInfo.environment["UI_TEST_FIXTURE"]
@@ -93,8 +99,9 @@ enum UITestMode {
     @MainActor
     private static func resetAppState() {
         let defaults = GroupUserDefaults.groupDefaults
-        // Clear group user defaults using the suite domain name
+        // Clear group user defaults using the session-specific or shared suite domain name
-        defaults.removePersistentDomain(forName: Constants.currentGroupShareId)
+        let suiteName = GroupUserDefaults.currentSuiteName
+        defaults.removePersistentDomain(forName: suiteName)
 
         // Explicitly clear subscription cache keys that may survive removePersistentDomain
         // on app group suites (known reliability issue).

Tests iOS/AccessibilityTextSizeTests.swift

@@ -10,25 +10,8 @@ import XCTest
 final class AccessibilityTextSizeTests: BaseUITestCase {
     override var seedFixture: String? { "single_mood" }
     override var bypassSubscription: Bool { true }
-
+    override var extraLaunchArguments: [String] {
-    override func setUp() {
+        ["-UIPreferredContentSizeCategoryName", "UICTContentSizeCategoryAccessibilityXXL"]
-        // Do NOT call super — we need custom content size launch args
-        continueAfterFailure = false
-
-        let application = XCUIApplication()
-        var args: [String] = [
-            "--ui-testing", "--disable-animations",
-            "--reset-state",
-            "--bypass-subscription",
-            "--skip-onboarding",
-            "-AppleLanguages", "(en)",
-            "-AppleLocale", "en_US",
-            "-UIPreferredContentSizeCategoryName", "UICTContentSizeCategoryAccessibilityXXL"
-        ]
-        application.launchArguments = args
-        application.launchEnvironment = ["UI_TEST_FIXTURE": "single_mood"]
-        application.launch()
-        app = application
     }
 
     /// TC-142: App launches and is navigable at largest accessibility text size.

Tests iOS/DateLocaleTests.swift

@@ -10,25 +10,7 @@ import XCTest
 final class DateLocaleTests: BaseUITestCase {
     override var seedFixture: String? { "week_of_moods" }
     override var bypassSubscription: Bool { true }
-
+    override var localeArguments: [String] { ["-AppleLanguages", "(de)", "-AppleLocale", "de_DE"] }
-    override func setUp() {
-        // Do NOT call super — we need custom locale launch args
-        continueAfterFailure = false
-
-        let application = XCUIApplication()
-        let args: [String] = [
-            "--ui-testing", "--disable-animations",
-            "--reset-state",
-            "--bypass-subscription",
-            "--skip-onboarding",
-            "-AppleLanguages", "(de)",
-            "-AppleLocale", "de_DE"
-        ]
-        application.launchArguments = args
-        application.launchEnvironment = ["UI_TEST_FIXTURE": "week_of_moods"]
-        application.launch()
-        app = application
-    }
 
     /// TC-139: German locale displays German month/weekday names.
     func testGermanLocale_DateFormattingMatchesLocale() {

Tests iOS/Helpers/BaseUITestCase.swift

@@ -3,7 +3,8 @@
 //  Tests iOS
 //
 //  Base class for all UI tests. Handles launch arguments,
-//  state reset, and screenshot capture on failure.
+//  state reset, screenshot capture on failure, and parallel
+//  test isolation via per-session data sandboxing.
 //
 
 import XCTest
@@ -12,6 +13,13 @@ class BaseUITestCase: XCTestCase {
 
     var app: XCUIApplication!
 
+    // MARK: - Parallel Test Isolation
+
+    /// Unique session ID for this test class instance.
+    /// Passed to the app via environment so each parallel runner gets
+    /// its own UserDefaults suite and in-memory SwiftData container.
+    private(set) var testSessionID: String = UUID().uuidString
+
     // MARK: - Configuration (override in subclasses)
 
     /// Fixture to seed. Override to use a specific data set.
@@ -26,6 +34,15 @@ class BaseUITestCase: XCTestCase {
     /// Whether to force the trial to be expired. Default: false.
     var expireTrial: Bool { false }
 
+    /// Override to change the test locale/language.
+    /// Default: English (US). Locale tests override this instead of setUp().
+    var localeArguments: [String] { ["-AppleLanguages", "(en)", "-AppleLocale", "en_US"] }
+
+    /// Extra launch arguments for tests needing special settings
+    /// (accessibility sizes, reduce motion, high contrast, etc.).
+    /// Override in subclasses instead of overriding setUp().
+    var extraLaunchArguments: [String] { [] }
+
     // MARK: - Lifecycle
 
     override func setUp() {
@@ -46,7 +63,8 @@ class BaseUITestCase: XCTestCase {
     // MARK: - Launch Configuration
 
     private func buildLaunchArguments(resetState: Bool) -> [String] {
-        var args = ["--ui-testing", "--disable-animations", "-AppleLanguages", "(en)", "-AppleLocale", "en_US"]
+        var args = ["--ui-testing", "--disable-animations"]
+        args.append(contentsOf: localeArguments)
         if resetState {
             args.append("--reset-state")
         }
@@ -59,11 +77,13 @@ class BaseUITestCase: XCTestCase {
         if expireTrial {
             args.append("--expire-trial")
         }
+        args.append(contentsOf: extraLaunchArguments)
         return args
     }
 
     private func buildLaunchEnvironment() -> [String: String] {
         var env = [String: String]()
+        env["UI_TEST_SESSION_ID"] = testSessionID
         if let fixture = seedFixture {
             env["UI_TEST_FIXTURE"] = fixture
         }
@@ -90,6 +110,26 @@ class BaseUITestCase: XCTestCase {
         return application
     }
 
+    /// Relaunch the app with custom bypass setting, preserving the session ID.
+    /// Use when a test needs to toggle subscription bypass mid-test.
+    @discardableResult
+    func relaunchApp(resetState: Bool, bypassSubscription overrideBypass: Bool) -> XCUIApplication {
+        app.terminate()
+        let application = XCUIApplication()
+        var args = ["--ui-testing", "--disable-animations"]
+        args.append(contentsOf: localeArguments)
+        if resetState { args.append("--reset-state") }
+        if overrideBypass { args.append("--bypass-subscription") }
+        if skipOnboarding { args.append("--skip-onboarding") }
+        if expireTrial { args.append("--expire-trial") }
+        args.append(contentsOf: extraLaunchArguments)
+        application.launchArguments = args
+        application.launchEnvironment = buildLaunchEnvironment()
+        application.launch()
+        app = application
+        return application
+    }
+
     @discardableResult
     func relaunchPreservingState() -> XCUIApplication {
         app.terminate()

Tests iOS/HierarchyDumpTest.swift

@@ -1,19 +1,18 @@
 import XCTest
 
-class HierarchyDumpTest: XCTestCase {
+class HierarchyDumpTest: BaseUITestCase {
+    override var seedFixture: String? { nil }
+
     func testDumpAccessibilityTree() {
-        let app = XCUIApplication()
-        app.launchArguments = ["--ui-testing", "--reset-state", "--disable-animations", "--bypass-subscription", "--skip-onboarding"]
-        app.launch()
         sleep(3)
 
         print("\n=== ELEMENT QUERIES ===")
-        print("otherElements[mood_header]: \(app.otherElements[\"mood_header\"].exists)")
+        print("otherElements[mood_header]: \(app.otherElements["mood_header"].exists)")
-        print("descendants[mood_header]: \(app.descendants(matching: .any)[\"mood_header\"].firstMatch.exists)")
+        print("descendants[mood_header]: \(app.descendants(matching: .any)["mood_header"].firstMatch.exists)")
-        print("groups[mood_header]: \(app.groups[\"mood_header\"].exists)")
+        print("groups[mood_header]: \(app.groups["mood_header"].exists)")
-        print("scrollViews[mood_header]: \(app.scrollViews[\"mood_header\"].exists)")
+        print("scrollViews[mood_header]: \(app.scrollViews["mood_header"].exists)")
-        print("staticTexts[mood_header]: \(app.staticTexts[\"mood_header\"].exists)")
+        print("staticTexts[mood_header]: \(app.staticTexts["mood_header"].exists)")
-        print("buttons[mood_button_great]: \(app.buttons[\"mood_button_great\"].exists)")
+        print("buttons[mood_button_great]: \(app.buttons["mood_button_great"].exists)")
         print("tabBars count: \(app.tabBars.count)")
         if app.tabBars.count > 0 {
             let tb = app.tabBars.firstMatch
@@ -21,7 +20,7 @@ class HierarchyDumpTest: XCTestCase {
                 print("  tab button: \(b.identifier) label=\(b.label)")
             }
         }
-        print("otherElements[settings_header]: \(app.otherElements[\"settings_header\"].exists)")
+        print("otherElements[settings_header]: \(app.otherElements["settings_header"].exists)")
 
         print("\n=== HIERARCHY (first 200 lines) ===")
         let desc = app.debugDescription

Tests iOS/HighContrastTests.swift

@@ -10,25 +10,8 @@ import XCTest
 final class HighContrastTests: BaseUITestCase {
     override var seedFixture: String? { "single_mood" }
     override var bypassSubscription: Bool { true }
-
+    override var extraLaunchArguments: [String] {
-    override func setUp() {
+        ["-UIAccessibilityDarkerSystemColorsEnabled", "YES"]
-        // Do NOT call super — we need custom accessibility launch args
-        continueAfterFailure = false
-
-        let application = XCUIApplication()
-        let args: [String] = [
-            "--ui-testing", "--disable-animations",
-            "--reset-state",
-            "--bypass-subscription",
-            "--skip-onboarding",
-            "-AppleLanguages", "(en)",
-            "-AppleLocale", "en_US",
-            "-UIAccessibilityDarkerSystemColorsEnabled", "YES"
-        ]
-        application.launchArguments = args
-        application.launchEnvironment = ["UI_TEST_FIXTURE": "single_mood"]
-        application.launch()
-        app = application
     }
 
     /// TC-144: App is navigable with High Contrast mode enabled.

Tests iOS/LongTranslationTests.swift

@@ -10,25 +10,7 @@ import XCTest
 final class LongTranslationTests: BaseUITestCase {
     override var seedFixture: String? { "single_mood" }
     override var bypassSubscription: Bool { true }
-
+    override var localeArguments: [String] { ["-AppleLanguages", "(de)", "-AppleLocale", "de_DE"] }
-    override func setUp() {
-        // Do NOT call super — we need German locale (known for long compound words)
-        continueAfterFailure = false
-
-        let application = XCUIApplication()
-        let args: [String] = [
-            "--ui-testing", "--disable-animations",
-            "--reset-state",
-            "--bypass-subscription",
-            "--skip-onboarding",
-            "-AppleLanguages", "(de)",
-            "-AppleLocale", "de_DE"
-        ]
-        application.launchArguments = args
-        application.launchEnvironment = ["UI_TEST_FIXTURE": "single_mood"]
-        application.launch()
-        app = application
-    }
 
     /// TC-138: German locale with long compound words renders without crashes.
     /// Navigates through all tabs to ensure no layout truncation causes issues.

Tests iOS/ReduceMotionTests.swift

@@ -10,25 +10,8 @@ import XCTest
 final class ReduceMotionTests: BaseUITestCase {
     override var seedFixture: String? { "single_mood" }
     override var bypassSubscription: Bool { true }
-
+    override var extraLaunchArguments: [String] {
-    override func setUp() {
+        ["-UIReduceMotionPreference", "YES"]
-        // Do NOT call super — we need custom accessibility launch args
-        continueAfterFailure = false
-
-        let application = XCUIApplication()
-        let args: [String] = [
-            "--ui-testing", "--disable-animations",
-            "--reset-state",
-            "--bypass-subscription",
-            "--skip-onboarding",
-            "-AppleLanguages", "(en)",
-            "-AppleLocale", "en_US",
-            "-UIReduceMotionPreference", "YES"
-        ]
-        application.launchArguments = args
-        application.launchEnvironment = ["UI_TEST_FIXTURE": "single_mood"]
-        application.launch()
-        app = application
     }
 
     /// TC-143: App is navigable with Reduce Motion enabled.

Tests iOS/SpanishLocalizationTests.swift

@@ -10,25 +10,7 @@ import XCTest
 final class SpanishLocalizationTests: BaseUITestCase {
     override var seedFixture: String? { "week_of_moods" }
     override var bypassSubscription: Bool { true }
-
+    override var localeArguments: [String] { ["-AppleLanguages", "(es)", "-AppleLocale", "es_ES"] }
-    override func setUp() {
-        // Do NOT call super — we need custom language launch args
-        continueAfterFailure = false
-
-        let application = XCUIApplication()
-        let args: [String] = [
-            "--ui-testing", "--disable-animations",
-            "--reset-state",
-            "--bypass-subscription",
-            "--skip-onboarding",
-            "-AppleLanguages", "(es)",
-            "-AppleLocale", "es_ES"
-        ]
-        application.launchArguments = args
-        application.launchEnvironment = ["UI_TEST_FIXTURE": "week_of_moods"]
-        application.launch()
-        app = application
-    }
 
     /// TC-137: Key Spanish strings appear when launched in Spanish locale.
     func testSpanishLocale_DisplaysSpanishStrings() {

Tests iOS/TrialBannerTests.swift

@@ -20,20 +20,8 @@ final class TrialBannerTests: BaseUITestCase {
         settingsScreen.assertVisible()
 
         // With default settings (bypassSubscription = true), the banner is hidden.
-        // We need to launch without bypass to see the banner.
+        // Re-launch without bypass to see the banner.
-        // Re-launch with bypass disabled.
+        relaunchApp(resetState: true, bypassSubscription: false)
-        app.terminate()
-
-        let freshApp = XCUIApplication()
-        var args = ["--ui-testing", "--reset-state", "--disable-animations", "--skip-onboarding",
-                    "-AppleLanguages", "(en)", "-AppleLocale", "en_US"]
-        // Do NOT add --bypass-subscription
-        freshApp.launchArguments = args
-        if let fixture = seedFixture {
-            freshApp.launchEnvironment = ["UI_TEST_FIXTURE": fixture]
-        }
-        freshApp.launch()
-        app = freshApp
 
         // Navigate to Settings
         let freshTabBar = TabBarScreen(app: app)