Write a test that proves issue #170

Tests/AuthFoundationTests/CredentialRefreshTests.swift

@@ -315,26 +315,55 @@ final class CredentialRefreshTests: XCTestCase, OAuth2ClientDelegate {
     @available(iOS 13.0, tvOS 13.0, macOS 10.15, watchOS 6, *)
     func testRefreshAsync() async throws {
         let credential = try credential(for: Token.simpleMockToken)
-        try await credential.refresh()
+        try perform {
+            try await credential.refresh()
+        }
     }
 
     @available(iOS 13.0, tvOS 13.0, macOS 10.15, watchOS 6, *)
     func testRefreshIfNeededExpiredAsync() async throws {
         let credential = try credential(for: Token.mockToken(issuedOffset: 6000))
-        try await credential.refreshIfNeeded(graceInterval: 300)
+        try perform {
+            try await credential.refreshIfNeeded(graceInterval: 300)
+        }
     }
 
     @available(iOS 13.0, tvOS 13.0, macOS 10.15, watchOS 6, *)
     func testRefreshIfNeededWithinGraceIntervalAsync() async throws {
         let credential = try credential(for: Token.mockToken(issuedOffset: 0),
                                            expectAPICalls: .none)
-        try await credential.refreshIfNeeded(graceInterval: 300)
+        try perform {
+            try await credential.refreshIfNeeded(graceInterval: 300)
+        }
     }
 
     @available(iOS 13.0, tvOS 13.0, macOS 10.15, watchOS 6, *)
     func testRefreshIfNeededOutsideGraceIntervalAsync() async throws {
-            let credential = try credential(for: Token.mockToken(issuedOffset: 3500))
-        try await credential.refreshIfNeeded(graceInterval: 300)
+        let credential = try credential(for: Token.mockToken(issuedOffset: 3500))
+        try perform {
+            try await credential.refreshIfNeeded(graceInterval: 300)
+        }
+    }
+
+    func perform(queueCount: Int = 5, iterationCount: Int = 10, _ block: @escaping () async throws -> Void) rethrows {
+        let queues: [DispatchQueue] = (0..<queueCount).map { queueNumber in
+            DispatchQueue(label: "Async queue \(queueNumber)")
+        }
+
+        let group = DispatchGroup()
+        for queue in queues {
+            for _ in 0..<iterationCount {
+                queue.async {
+                    group.enter()
+                    Task {
+                        try await block()
+                        group.leave()
+                    }
+                }
+            }
+        }
+
+        _ = group.wait(timeout: .short)
     }
     #endif
 }

Tests/TestCommon/TimeInterval+Extensions.swift

@@ -0,0 +1,27 @@
+//
+// Copyright (c) 2023-Present, Okta, Inc. and/or its affiliates. All rights reserved.
+// The Okta software accompanied by this notice is provided pursuant to the Apache License, Version 2.0 (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
+
+public extension TimeInterval {
+    static let standard: Self = 3
+    static let short: Self = 1
+    static let long: Self = 5
+    static let veryLong: Self = 10
+}
+
+public extension DispatchTime {
+    static var standard: Self { .now() + .standard }
+    static var short: Self { .now() + .short }
+    static var long: Self { .now() + .long }
+    static var veryLong: Self { .now() + .veryLong }
+}