diff --git a/Sources/LocalData/Helpers/SyncHelper.swift b/Sources/LocalData/Helpers/SyncHelper.swift
index c35b0d2..90bd629 100644
--- a/Sources/LocalData/Helpers/SyncHelper.swift
+++ b/Sources/LocalData/Helpers/SyncHelper.swift
@@ -128,8 +128,8 @@ actor SyncHelper {
     }
 }
 
-/// A private proxy class to handle WCSessionDelegate callbacks and route them to the SyncHelper actor.
-private final class SessionDelegateProxy: NSObject, WCSessionDelegate {
+/// An internal proxy class to handle WCSessionDelegate callbacks and route them to the SyncHelper actor.
+internal final class SessionDelegateProxy: NSObject, WCSessionDelegate {
     static let shared = SessionDelegateProxy()
     
     func session(_ session: WCSession, activationDidCompleteWith activationState: WCSessionActivationState, error: Error?) {
diff --git a/Tests/LocalDataTests/AppGroupTests.swift b/Tests/LocalDataTests/AppGroupTests.swift
index c9e241d..60d2935 100644
--- a/Tests/LocalDataTests/AppGroupTests.swift
+++ b/Tests/LocalDataTests/AppGroupTests.swift
@@ -53,4 +53,33 @@ import Testing
             }
         }
     }
+
+    @Test func fileStorageAppGroupRoundTrip() async throws {
+        // In simulator, this usually returns a placeholder path
+        let identifier = "group.com.test.localdata"
+        let fileName = "appgroup_file.txt"
+        let data = Data("appgroup-file-content".utf8)
+        
+        // Only run if the simulator/environment gives us a container
+        if let _ = FileManager.default.containerURL(forSecurityApplicationGroupIdentifier: identifier) {
+            try await fileStorageHelper.write(data, to: .documents, fileName: fileName, appGroupIdentifier: identifier)
+            
+            let exists = await fileStorageHelper.exists(in: .documents, fileName: fileName, appGroupIdentifier: identifier)
+            #expect(exists == true)
+            
+            let retrieved = try await fileStorageHelper.read(from: .documents, fileName: fileName, appGroupIdentifier: identifier)
+            #expect(retrieved == data)
+            
+            let list = try await fileStorageHelper.list(in: .documents, appGroupIdentifier: identifier)
+            #expect(list.contains(fileName))
+            
+            let size = try await fileStorageHelper.size(of: .documents, fileName: fileName, appGroupIdentifier: identifier)
+            #expect(size == Int64(data.count))
+            
+            try await fileStorageHelper.delete(from: .documents, fileName: fileName, appGroupIdentifier: identifier)
+            
+            let afterDelete = await fileStorageHelper.exists(in: .documents, fileName: fileName, appGroupIdentifier: identifier)
+            #expect(afterDelete == false)
+        }
+    }
 }
diff --git a/Tests/LocalDataTests/RouterDomainTests.swift b/Tests/LocalDataTests/RouterDomainTests.swift
new file mode 100644
index 0000000..bdf54c2
--- /dev/null
+++ b/Tests/LocalDataTests/RouterDomainTests.swift
@@ -0,0 +1,117 @@
+import Foundation
+import Testing
+@testable import LocalData
+
+@Suite struct RouterDomainTests {
+    private let router: StorageRouter
+    private let mockKeychain = MockKeychainHelper()
+    
+    init() {
+        let testBaseURL = FileManager.default.temporaryDirectory.appending(path: "RouterDomainTests-\(UUID().uuidString)")
+        router = StorageRouter(
+            keychain: mockKeychain,
+            encryption: EncryptionHelper(keychain: mockKeychain),
+            file: FileStorageHelper(configuration: FileStorageConfiguration(baseURL: testBaseURL)),
+            defaults: UserDefaultsHelper(defaults: UserDefaults(suiteName: "RouterDomainTests-\(UUID().uuidString)")!)
+        )
+    }
+    
+    private struct DomainKey: StorageKey {
+        typealias Value = String
+        let name: String
+        let domain: StorageDomain
+        let security: SecurityPolicy
+        let serializer: Serializer<String> = .json
+        let owner: String = "DomainTests"
+        let description: String = "Domain test key"
+        let availability: PlatformAvailability = .all
+        let syncPolicy: SyncPolicy = .never
+        
+        init(name: String, domain: StorageDomain, security: SecurityPolicy = .none) {
+            self.name = name
+            self.domain = domain
+            self.security = security
+        }
+    }
+    
+    @Test func domainUserDefaults() async throws {
+        let key = DomainKey(name: "defaults.key", domain: .userDefaults(suite: nil))
+        try await router.set("value", for: key)
+        #expect(try await router.get(key) == "value")
+        try await router.remove(key)
+        #expect(await (try? router.exists(key)) == false)
+    }
+    
+    @Test func domainAppGroupUserDefaults() async throws {
+        // We use a mock configuration to avoid requiring a real app group
+        await router.updateStorageConfiguration(StorageConfiguration(defaultAppGroupIdentifier: "group.test"))
+        
+        let key = DomainKey(name: "appgroup.defaults.key", domain: .appGroupUserDefaults(identifier: "group.test"))
+        try await router.set("value", for: key)
+        #expect(try await router.get(key) == "value")
+        try await router.remove(key)
+    }
+    
+    @Test func domainKeychain() async throws {
+        let key = DomainKey(
+            name: "keychain.key", 
+            domain: .keychain(service: "test"), 
+            security: .keychain(accessibility: .afterFirstUnlock, accessControl: .none)
+        )
+        try await router.set("value", for: key)
+        #expect(try await router.get(key) == "value")
+        try await router.remove(key)
+    }
+    
+    @Test func domainFileSystem() async throws {
+        let key = DomainKey(name: "file.key", domain: .fileSystem(directory: .documents))
+        try await router.set("value", for: key)
+        #expect(try await router.get(key) == "value")
+        try await router.remove(key)
+    }
+    
+    @Test func domainEncryptedFileSystem() async throws {
+        let key = DomainKey(name: "encfile.key", domain: .encryptedFileSystem(directory: .documents))
+        try await router.set("value", for: key)
+        #expect(try await router.get(key) == "value")
+        try await router.remove(key)
+    }
+    
+    @Test func domainAppGroupFileSystem() async throws {
+        // App blocks usually fail or return nil in tests, but we exercise the path
+        await router.updateStorageConfiguration(StorageConfiguration(defaultAppGroupIdentifier: "group.test"))
+        let key = DomainKey(name: "appgroup.file.key", domain: .appGroupFileSystem(identifier: "group.test", directory: .documents))
+        
+        do {
+            try await router.set("value", for: key)
+            #expect(try await router.get(key) == "value")
+            try await router.remove(key)
+        } catch StorageError.invalidAppGroupIdentifier {
+            // Path covered
+        }
+    }
+
+    @Test func resolutionFailureService() async throws {
+        // Clear default service
+        await router.updateStorageConfiguration(StorageConfiguration(defaultKeychainService: nil))
+        let key = DomainKey(
+            name: "bad.service.key", 
+            domain: .keychain(service: nil),
+            security: .keychain(accessibility: .afterFirstUnlock, accessControl: .none)
+        )
+        
+        await #expect(throws: StorageError.keychainError(errSecBadReq)) {
+            try await router.set("value", for: key)
+        }
+    }
+
+    @Test func resolutionFailureIdentifier() async throws {
+        // Clear default identifier
+        await router.updateStorageConfiguration(StorageConfiguration(defaultAppGroupIdentifier: nil))
+        let key = DomainKey(name: "bad.id.key", domain: .appGroupUserDefaults(identifier: nil))
+        
+        await #expect(throws: StorageError.invalidAppGroupIdentifier("none")) {
+            try await router.set("value", for: key)
+        }
+    }
+}
diff --git a/Tests/LocalDataTests/RouterSecurityTests.swift b/Tests/LocalDataTests/RouterSecurityTests.swift
new file mode 100644
index 0000000..c892bdb
--- /dev/null
+++ b/Tests/LocalDataTests/RouterSecurityTests.swift
@@ -0,0 +1,92 @@
+import Foundation
+import Testing
+import Security
+@testable import LocalData
+
+@Suite struct RouterSecurityTests {
+    private let router: StorageRouter
+    private let mockKeychain = MockKeychainHelper()
+    
+    init() {
+        let testBaseURL = FileManager.default.temporaryDirectory.appending(path: "RouterSecurityTests-\(UUID().uuidString)")
+        router = StorageRouter(
+            keychain: mockKeychain,
+            encryption: EncryptionHelper(keychain: mockKeychain),
+            file: FileStorageHelper(configuration: FileStorageConfiguration(baseURL: testBaseURL)),
+            defaults: UserDefaultsHelper(defaults: UserDefaults(suiteName: "RouterSecurityTests-\(UUID().uuidString)")!)
+        )
+    }
+    
+    private struct SecurityKey: StorageKey {
+        typealias Value = String
+        let name: String
+        let domain: StorageDomain
+        let security: SecurityPolicy
+        let serializer: Serializer<String> = .json
+        let owner: String = "SecurityTests"
+        let description: String = "Security test key"
+        let availability: PlatformAvailability = .all
+        let syncPolicy: SyncPolicy = .never
+    }
+    
+    @Test func applySecurityNone() async throws {
+        let key = SecurityKey(name: "none.key", domain: .userDefaults(suite: nil), security: .none)
+        let value = "test-value"
+        
+        try await router.set(value, for: key)
+        let retrieved: String = try await router.get(key)
+        #expect(retrieved == value)
+    }
+    
+    @Test func applySecurityEncryptedAES() async throws {
+        let key = SecurityKey(
+            name: "aes.key", 
+            domain: .userDefaults(suite: nil), 
+            security: .encrypted(.aes256(keyDerivation: .hkdf()))
+        )
+        let value = "aes-secret"
+        
+        try await router.set(value, for: key)
+        let retrieved: String = try await router.get(key)
+        #expect(retrieved == value)
+    }
+    
+    @Test func applySecurityEncryptedChaCha() async throws {
+        let key = SecurityKey(
+            name: "chacha.key", 
+            domain: .userDefaults(suite: nil), 
+            security: .encrypted(.chacha20Poly1305(keyDerivation: .hkdf()))
+        )
+        let value = "chacha-secret"
+        
+        try await router.set(value, for: key)
+        let retrieved: String = try await router.get(key)
+        #expect(retrieved == value)
+    }
+    
+    @Test func applySecurityKeychain() async throws {
+        let key = SecurityKey(
+            name: "keychain.key", 
+            domain: .keychain(service: "test-service"), 
+            security: .keychain(accessibility: .afterFirstUnlock, accessControl: .none)
+        )
+        let value = "keychain-secret"
+        
+        try await router.set(value, for: key)
+        let retrieved: String = try await router.get(key)
+        #expect(retrieved == value)
+    }
+
+    @Test func applySecurityPBKDF2() async throws {
+        let key = SecurityKey(
+            name: "pbkdf2.key", 
+            domain: .userDefaults(suite: nil), 
+            security: .encrypted(.aes256(keyDerivation: .pbkdf2()))
+        )
+        let value = "pbkdf2-secret"
+        
+        try await router.set(value, for: key)
+        let retrieved: String = try await router.get(key)
+        #expect(retrieved == value)
+    }
+}
diff --git a/Tests/LocalDataTests/SyncDelegateTests.swift b/Tests/LocalDataTests/SyncDelegateTests.swift
new file mode 100644
index 0000000..9b2e56e
--- /dev/null
+++ b/Tests/LocalDataTests/SyncDelegateTests.swift
@@ -0,0 +1,43 @@
+import Foundation
+import Testing
+import WatchConnectivity
+@testable import LocalData
+
+@Suite struct SyncDelegateTests {
+    
+    @Test func delegateProxyActivationCallbacks() {
+        let proxy = SessionDelegateProxy.shared
+        let session = WCSession.default
+        
+        // Exercise activation completion (success)
+        proxy.session(session, activationDidCompleteWith: .activated, error: nil)
+        
+        // Exercise activation completion (error)
+        let error = NSError(domain: "test", code: 1, userInfo: nil)
+        proxy.session(session, activationDidCompleteWith: .notActivated, error: error)
+    }
+    
+    @Test func delegateProxyContextReceived() async throws {
+        let proxy = SessionDelegateProxy.shared
+        let session = WCSession.default
+        let context: [String: Any] = [
+            "test.sync.key": Data("sync-data".utf8)
+        ]
+        
+        // This triggers SyncHelper.handleReceivedContext
+        proxy.session(session, didReceiveApplicationContext: context)
+        
+        // Wait a bit for the Task to start/finish
+        try await Task.sleep(for: .milliseconds(100))
+    }
+    
+    #if os(iOS)
+    @Test func delegateProxyiOSCallbacks() {
+        let proxy = SessionDelegateProxy.shared
+        let session = WCSession.default
+        
+        proxy.sessionDidBecomeInactive(session)
+        proxy.sessionDidDeactivate(session)
+    }
+    #endif
+}