diff --git a/FirebaseRemoteConfig/Tests/SwiftUnit/UserDefaultsManagerOrigTests.swift b/FirebaseRemoteConfig/Tests/SwiftUnit/UserDefaultsManagerOrigTests.swift
new file mode 100644
index 00000000000..07f2c2f4dd1
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+++ b/FirebaseRemoteConfig/Tests/SwiftUnit/UserDefaultsManagerOrigTests.swift
@@ -0,0 +1,245 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+@testable import FirebaseRemoteConfig
+import XCTest
+
+private let appName = "testApp"
+private let fqNamespace1 = "testNamespace1:testApp"
+private let fqNamespace2 = "testNamespace2:testApp"
+private var userDefaultsSampleTimestamp: TimeInterval = 0
+
+class UserDefaultsManagerOrigTests: XCTestCase {
+  private var bundleID: String!
+
+  override func setUp() async throws {
+    try await super.setUp()
+    // Clear UserDefaults before each test.
+    bundleID = try XCTUnwrap(Bundle.main.bundleIdentifier)
+    userDefaultsSampleTimestamp = Date().timeIntervalSince1970
+    UserDefaults.standard.removePersistentDomain(forName: bundleID)
+  }
+
+  func testUserDefaultsEtagWriteAndRead() {
+    let manager = UserDefaultsManager(appName: appName,
+                                      bundleID: bundleID,
+                                      namespace: fqNamespace1)
+    manager.lastETag = "eTag1"
+    XCTAssertEqual(manager.lastETag, "eTag1")
+
+    manager.lastETag = "eTag2"
+    XCTAssertEqual(manager.lastETag, "eTag2")
+  }
+
+  func testUserDefaultsLastFetchTimeWriteAndRead() {
+    let manager = UserDefaultsManager(appName: appName,
+                                      bundleID: bundleID,
+                                      namespace: fqNamespace1)
+    manager.lastFetchTime = userDefaultsSampleTimestamp
+    XCTAssertEqual(manager.lastFetchTime, userDefaultsSampleTimestamp)
+
+    manager.lastFetchTime = userDefaultsSampleTimestamp - 1000
+    XCTAssertEqual(manager.lastFetchTime, userDefaultsSampleTimestamp - 1000)
+  }
+
+  func testUserDefaultsLastETagUpdateTimeWriteAndRead() {
+    let manager = UserDefaultsManager(appName: appName,
+                                      bundleID: bundleID,
+                                      namespace: fqNamespace1)
+    manager.lastETagUpdateTime = userDefaultsSampleTimestamp
+    XCTAssertEqual(manager.lastETagUpdateTime, userDefaultsSampleTimestamp)
+
+    manager.lastETagUpdateTime = userDefaultsSampleTimestamp - 1000
+    XCTAssertEqual(manager.lastETagUpdateTime, userDefaultsSampleTimestamp - 1000)
+  }
+
+  func testUserDefaultsLastFetchStatusWriteAndRead() {
+    let manager = UserDefaultsManager(appName: appName,
+                                      bundleID: bundleID,
+                                      namespace: fqNamespace1)
+    manager.lastFetchStatus = "Success"
+    XCTAssertEqual(manager.lastFetchStatus, "Success")
+
+    manager.lastFetchStatus = "Error"
+    XCTAssertEqual(manager.lastFetchStatus, "Error")
+  }
+
+  func testUserDefaultsIsClientThrottledWriteAndRead() {
+    let manager = UserDefaultsManager(appName: appName,
+                                      bundleID: bundleID,
+                                      namespace: fqNamespace1)
+    manager.isClientThrottledWithExponentialBackoff = true
+    XCTAssertEqual(manager.isClientThrottledWithExponentialBackoff, true)
+
+    manager.isClientThrottledWithExponentialBackoff = false
+    XCTAssertEqual(manager.isClientThrottledWithExponentialBackoff, false)
+  }
+
+  func testUserDefaultsThrottleEndTimeWriteAndRead() {
+    let manager = UserDefaultsManager(appName: appName,
+                                      bundleID: bundleID,
+                                      namespace: fqNamespace1)
+
+    manager.throttleEndTime = userDefaultsSampleTimestamp - 7.0
+    XCTAssertEqual(manager.throttleEndTime, userDefaultsSampleTimestamp - 7.0)
+
+    manager.throttleEndTime = userDefaultsSampleTimestamp - 8.0
+    XCTAssertEqual(manager.throttleEndTime, userDefaultsSampleTimestamp - 8.0)
+  }
+
+  func testUserDefaultsCurrentThrottlingRetryIntervalWriteAndRead() {
+    let manager = UserDefaultsManager(appName: appName,
+                                      bundleID: bundleID,
+                                      namespace: fqNamespace1)
+    manager.currentThrottlingRetryIntervalSeconds = userDefaultsSampleTimestamp - 1.0
+    XCTAssertEqual(
+      manager.currentThrottlingRetryIntervalSeconds,
+      userDefaultsSampleTimestamp - 1.0
+    )
+
+    manager.currentThrottlingRetryIntervalSeconds = userDefaultsSampleTimestamp - 2.0
+    XCTAssertEqual(
+      manager.currentThrottlingRetryIntervalSeconds,
+      userDefaultsSampleTimestamp - 2.0
+    )
+  }
+
+  func testUserDefaultsTemplateVersionWriteAndRead() {
+    let manager = UserDefaultsManager(appName: appName,
+                                      bundleID: bundleID,
+                                      namespace: fqNamespace1)
+    manager.lastFetchedTemplateVersion = "1"
+    XCTAssertEqual(manager.lastFetchedTemplateVersion, "1")
+  }
+
+  func testUserDefaultsActiveTemplateVersionWriteAndRead() {
+    let manager = UserDefaultsManager(appName: appName,
+                                      bundleID: bundleID,
+                                      namespace: fqNamespace1)
+    manager.lastActiveTemplateVersion = "1"
+    XCTAssertEqual(manager.lastActiveTemplateVersion, "1")
+  }
+
+  func testUserDefaultsRealtimeThrottleEndTimeWriteAndRead() {
+    let manager = UserDefaultsManager(
+      appName: appName,
+      bundleID: bundleID,
+      namespace: fqNamespace1
+    )
+
+    manager.realtimeThrottleEndTime = userDefaultsSampleTimestamp - 7.0
+    XCTAssertEqual(manager.realtimeThrottleEndTime, userDefaultsSampleTimestamp - 7.0)
+
+    manager.realtimeThrottleEndTime = userDefaultsSampleTimestamp - 8.0
+    XCTAssertEqual(manager.realtimeThrottleEndTime, userDefaultsSampleTimestamp - 8.0)
+  }
+
+  func testUserDefaultsCurrentRealtimeThrottlingRetryIntervalWriteAndRead() {
+    let manager = UserDefaultsManager(appName: appName,
+                                      bundleID: bundleID,
+                                      namespace: fqNamespace1)
+    manager.currentRealtimeThrottlingRetryIntervalSeconds = userDefaultsSampleTimestamp - 1.0
+    XCTAssertEqual(manager.currentRealtimeThrottlingRetryIntervalSeconds,
+                   userDefaultsSampleTimestamp - 1.0)
+
+    manager.currentRealtimeThrottlingRetryIntervalSeconds = userDefaultsSampleTimestamp - 2.0
+    XCTAssertEqual(manager.currentRealtimeThrottlingRetryIntervalSeconds,
+                   userDefaultsSampleTimestamp - 2.0)
+  }
+
+  func testUserDefaultsForMultipleNamespaces() {
+    let manager1 = UserDefaultsManager(appName: appName,
+                                       bundleID: bundleID,
+                                       namespace: fqNamespace1)
+    let manager2 = UserDefaultsManager(appName: appName,
+                                       bundleID: bundleID,
+                                       namespace: fqNamespace2)
+
+    manager1.lastETag = "eTag1ForNamespace1"
+    manager2.lastETag = "eTag1ForNamespace2"
+    XCTAssertEqual(manager1.lastETag, "eTag1ForNamespace1")
+    XCTAssertEqual(manager2.lastETag, "eTag1ForNamespace2")
+
+    manager1.lastFetchTime = userDefaultsSampleTimestamp - 1000
+    manager2.lastFetchTime = userDefaultsSampleTimestamp - 7000
+    XCTAssertEqual(manager1.lastFetchTime, userDefaultsSampleTimestamp - 1000)
+    XCTAssertEqual(manager2.lastFetchTime, userDefaultsSampleTimestamp - 7000)
+
+    manager1.lastFetchStatus = "Success"
+    manager2.lastFetchStatus = "Error"
+    XCTAssertEqual(manager1.lastFetchStatus, "Success")
+    XCTAssertEqual(manager2.lastFetchStatus, "Error")
+
+    manager1.isClientThrottledWithExponentialBackoff = true
+    manager2.isClientThrottledWithExponentialBackoff = false
+    XCTAssertEqual(manager1.isClientThrottledWithExponentialBackoff, true)
+    XCTAssertEqual(manager2.isClientThrottledWithExponentialBackoff, false)
+
+    manager1.throttleEndTime = userDefaultsSampleTimestamp - 7.0
+    manager2.throttleEndTime = userDefaultsSampleTimestamp - 8.0
+    XCTAssertEqual(manager1.throttleEndTime, userDefaultsSampleTimestamp - 7.0)
+    XCTAssertEqual(manager2.throttleEndTime, userDefaultsSampleTimestamp - 8.0)
+
+    manager1.currentThrottlingRetryIntervalSeconds = userDefaultsSampleTimestamp - 1.0
+    manager2.currentThrottlingRetryIntervalSeconds = userDefaultsSampleTimestamp - 2.0
+    XCTAssertEqual(
+      manager1.currentThrottlingRetryIntervalSeconds,
+      userDefaultsSampleTimestamp - 1.0
+    )
+    XCTAssertEqual(
+      manager2.currentThrottlingRetryIntervalSeconds,
+      userDefaultsSampleTimestamp - 2.0
+    )
+
+    manager1.realtimeThrottleEndTime = userDefaultsSampleTimestamp - 7.0
+    manager2.realtimeThrottleEndTime = userDefaultsSampleTimestamp - 8.0
+    XCTAssertEqual(manager1.realtimeThrottleEndTime, userDefaultsSampleTimestamp - 7.0)
+    XCTAssertEqual(manager2.realtimeThrottleEndTime, userDefaultsSampleTimestamp - 8.0)
+
+    manager1.currentRealtimeThrottlingRetryIntervalSeconds = userDefaultsSampleTimestamp - 1.0
+    manager2.currentRealtimeThrottlingRetryIntervalSeconds = userDefaultsSampleTimestamp - 2.0
+    XCTAssertEqual(
+      manager1.currentRealtimeThrottlingRetryIntervalSeconds,
+      userDefaultsSampleTimestamp - 1.0
+    )
+    XCTAssertEqual(
+      manager2.currentRealtimeThrottlingRetryIntervalSeconds,
+      userDefaultsSampleTimestamp - 2.0
+    )
+
+    manager1.realtimeRetryCount = 1
+    manager2.realtimeRetryCount = 2
+    XCTAssertEqual(manager1.realtimeRetryCount, 1)
+    XCTAssertEqual(manager2.realtimeRetryCount, 2)
+
+    manager1.lastFetchedTemplateVersion = "1"
+    manager2.lastFetchedTemplateVersion = "2"
+    XCTAssertEqual(manager1.lastFetchedTemplateVersion, "1")
+    XCTAssertEqual(manager2.lastFetchedTemplateVersion, "2")
+
+    manager1.lastActiveTemplateVersion = "1"
+    manager2.lastActiveTemplateVersion = "2"
+    XCTAssertEqual(manager1.lastActiveTemplateVersion, "1")
+    XCTAssertEqual(manager2.lastActiveTemplateVersion, "2")
+  }
+
+  func testUserDefaultsReset() {
+    let manager = UserDefaultsManager(appName: appName,
+                                      bundleID: bundleID,
+                                      namespace: fqNamespace1)
+    manager.lastETag = "testETag"
+    manager.resetUserDefaults()
+    XCTAssertNil(manager.lastETag)
+  }
+}