diff --git a/PadelClubDataTests/PadelClubDataTests.swift b/PadelClubDataTests/PadelClubDataTests.swift
index d843bdb..aa986c3 100644
--- a/PadelClubDataTests/PadelClubDataTests.swift
+++ b/PadelClubDataTests/PadelClubDataTests.swift
@@ -11,6 +11,7 @@ import Testing
 
 enum TestError: Error {
     case notAuthenticated
+    case sameDeviceId
 }
 
 struct PadelClubDataTests {
diff --git a/PadelClubDataTests/SynchronizationTests.swift b/PadelClubDataTests/SynchronizationTests.swift
index 06e117a..6ca7137 100644
--- a/PadelClubDataTests/SynchronizationTests.swift
+++ b/PadelClubDataTests/SynchronizationTests.swift
@@ -22,6 +22,8 @@ struct SynchronizationTests {
         self.secondStoreCenter.configureURLs(secureScheme: false, domain: "127.0.0.1:8000", webSockets: false)
         self.secondStoreCenter.tokenKeychain = MockKeychainStore(fileName: "storage-2/token.json")
         self.secondStoreCenter.deviceKeychain = MockKeychainStore(fileName: "storage-2/device.json")
+        try self.secondStoreCenter.deviceKeychain.add(value: UUID().uuidString)
+        
         self.secondStoreCenter.classProject = "PadelClubData"
         
         let token2 = try? self.secondStoreCenter.rawTokenShouldNotBeUsed()
@@ -32,6 +34,7 @@ struct SynchronizationTests {
         StoreCenter.main.configureURLs(secureScheme: false, domain: "127.0.0.1:8000", webSockets: false)
         StoreCenter.main.tokenKeychain = MockKeychainStore(fileName: "storage/token.json")
         StoreCenter.main.deviceKeychain = MockKeychainStore(fileName: "storage/device.json")
+        try StoreCenter.main.deviceKeychain.add(value: UUID().uuidString)
         StoreCenter.main.classProject = "PadelClubData"
         
         let token = try? StoreCenter.main.rawTokenShouldNotBeUsed()
@@ -44,6 +47,11 @@ struct SynchronizationTests {
         let _: CustomUser = try await storeCenter.service().login(username: self.username, password: self.password)
     }
     
+    @Test("device id tests")
+    func testDeviceIds() async throws {
+        #expect(StoreCenter.main.deviceId() != self.secondStoreCenter.deviceId())
+    }
+    
     @Test func testAuthentication() {
         #expect(StoreCenter.main.isAuthenticated)
         #expect(self.secondStoreCenter.isAuthenticated)
@@ -56,10 +64,13 @@ struct SynchronizationTests {
         }
         
         // Cleanup
-        let eventCollection1: SyncedCollection<Event> =  StoreCenter.main.mainStore.registerSynchronizedCollection(synchronousLoading: true)
+        let eventCollection1: SyncedCollection<Event> = await StoreCenter.main.mainStore.synchronizedCollectionWithFileLoading()
+        #expect(eventCollection1.hasLoaded == true)
+        
         await eventCollection1.deleteAsync(contentOfs: Array(eventCollection1))
         
-        let eventCollection2: SyncedCollection<Event> =  self.secondStoreCenter.mainStore.registerSynchronizedCollection(synchronousLoading: true)
+        let eventCollection2: SyncedCollection<Event> = await  self.secondStoreCenter.mainStore.synchronizedCollectionWithFileLoading()
+        #expect(eventCollection2.hasLoaded == true)
         eventCollection2.clear()
 
         // Create
@@ -72,7 +83,7 @@ struct SynchronizationTests {
         try await eventCollection1.loadDataFromServerIfAllowed(clear: true)
         #expect(eventCollection1.count == 1)
         
-        try await eventCollection2.loadDataFromServerIfAllowed(clear: true)
+        try await self.secondStoreCenter.testSynchronizeOnceAsync()
         #expect(eventCollection2.count == 1)
         
         try await self.secondStoreCenter.testSynchronizeOnceAsync()