Add date wrapper to common dir

Author: ncooke3

FirebaseCore/Internal/Tests/Common/AdjustableDate.swift

@@ -0,0 +1,23 @@
+// Copyright 2024 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.
+
+import Foundation
+
+/// Used to manipulate a date across multiple concurrent contexts for simulation purposes.
+final class AdjustableDate: @unchecked Sendable {
+  var date: Date
+  init(date: Date) {
+    self.date = date
+  }
+}

FirebaseCore/Internal/Tests/Unit/HeartbeatControllerTests.swift

@@ -15,14 +15,6 @@
 @testable import FirebaseCoreInternal
 import XCTest
 
-/// Used to manipulate a date across multiple concurrent contexts for simulation purposes.
-final class AdjustableDate: @unchecked Sendable {
-  var date: Date
-  init(date: Date) {
-    self.date = date
-  }
-}
-
 class HeartbeatControllerTests: XCTestCase {
   // 2021-11-01 @ 00:00:00 (EST)
   let date = Date(timeIntervalSince1970: 1_635_739_200)