[tests] add a test for Property Executor Concurrency

* Add test `testPropertyExecutorConcurrency`

Author: nan-li

iOS_SDK/OneSignalSDK/OneSignalUserTests/OneSignalUserTests.swift

@@ -175,6 +175,44 @@ final class OneSignalUserTests: XCTestCase {
         XCTAssertTrue(client.allRequestsHandled)
     }
 
+    /**
+     This test aims to ensure concurrency safety in the Property Executor.
+     It is possible for two threads to modify and cache queues concurrently.
+     */
+    func testPropertyExecutorConcurrency() throws {
+        /* Setup */
+        let client = MockOneSignalClient()
+        // Ensure all requests fire the executor's callback so it will modify queues and cache it
+        client.fireSuccessForAllRequests = true
+        OneSignalCoreImpl.setSharedClient(client)
+
+        let identityModel = OSIdentityModel(aliases: [OS_ONESIGNAL_ID: UUID().uuidString], changeNotifier: OSEventProducer())
+        OneSignalUserManagerImpl.sharedInstance.addIdentityModelToRepo(identityModel)
+
+        let executor = OSPropertyOperationExecutor()
+        OSOperationRepo.sharedInstance.addExecutor(executor)
+
+        /* When */
+
+        DispatchQueue.concurrentPerform(iterations: 50) { _ in
+            // 1. Enqueue Deltas to the Operation Repo
+            OSOperationRepo.sharedInstance.enqueueDelta(OSDelta(name: OS_UPDATE_PROPERTIES_DELTA, identityModelId: identityModel.modelId, model: OSPropertiesModel(changeNotifier: OSEventProducer()), property: "language", value: UUID().uuidString))
+            OSOperationRepo.sharedInstance.enqueueDelta(OSDelta(name: OS_UPDATE_PROPERTIES_DELTA, identityModelId: identityModel.modelId, model: OSPropertiesModel(changeNotifier: OSEventProducer()), property: "language", value: UUID().uuidString))
+
+            // 2. Flush Operation Repo
+            OSOperationRepo.sharedInstance.addFlushDeltaQueueToDispatchQueue()
+
+            // 3. Simulate updating the executor's request queue from a network response
+            executor.executeUpdatePropertiesRequest(OSRequestUpdateProperties(params: ["properties": ["language": UUID().uuidString], "refresh_device_metadata": false], identityModel: identityModel), inBackground: false)
+        }
+
+        // 4. Run background threads
+        OneSignalCoreMocks.waitForBackgroundThreads(seconds: 0.5)
+
+        /* Then */
+        // No crash
+    }
+
     /**
      This test aims to ensure concurrency safety in the User Executor.
      It is possible for two threads to modify and cache queues concurrently.