Adopt SwiftTesting to improve test and runtime stability

[AlexNachbaur]

Begin migrating the Swift SDK to use the new SwiftTesting framework, away from the legacy XCTest toolchain. This has a few advantages:

• Improve stability, reliability, and performance of unit test runs
• Helps to identify runtime errors and concurrency gaps, simplifying mocking and shared state isolation in tests, which can also help runtime stability
• Better support tests in other non-Darwin runtime environments (e.g. Linux, Android, etc)

[Copilot]

Pull Request Overview

This PR adopts SwiftTesting framework to replace XCTest throughout the test suite, aiming to improve test stability and runtime performance. The migration includes removing XCTestCase dependencies, converting test assertions to SwiftTesting syntax, and introducing trait-based test configuration for better test isolation and reusability.

• Converts all test files from XCTest to SwiftTesting framework
• Introduces trait-based test configuration system for better test isolation
• Refactors test utilities to work with both XCTest and SwiftTesting
• Improves concurrent testing capabilities with new helper functions

Reviewed Changes

Copilot reviewed 106 out of 106 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
Tests/TestCommon/XCTestCase+Extensions.swift	Converts XCTestCase extension methods to standalone public functions
Tests/TestCommon/URLSessionMock.swift	Adds UUID to queue label and new requests filtering method
Tests/TestCommon/Traits/*.swift	Introduces SwiftTesting traits for test configuration and dependency injection
Tests/TestCommon/SwiftTesting+Extensions.swift	Adds new helper functions for async testing with confirmations
Tests/TestCommon/TimeInterval+Extensions.swift	Adds new accuracy comparison methods for TimeInterval and Int
Tests/TestCommon/MockTimeCoordinator.swift	New mock time coordinator for testing time-dependent functionality
Tests/*/*Tests.swift	Converts all test files from XCTest to SwiftTesting syntax

Comments suppressed due to low confidence (2)

Tests/TestCommon/XCTestCase+Extensions.swift:178

• [nitpick] The function name performConcurrent should be more descriptive. Consider renaming it to performConcurrentTests or runConcurrentOperations to better indicate its purpose.

public func performConcurrent(queueCount: Int = ProcessInfo.processInfo.activeProcessorCount,

Tests/AuthFoundationTests/TokenTests.swift:36

• [nitpick] The parameter name test is ambiguous. Consider renaming it to body or operation to better indicate that it's the test closure to execute within the configured environment.

    func withTokenTestEnvironment<T>(_ test: (OpenIdConfiguration) throws -> T) throws -> T {

[Copilot]

Using async initializers can be problematic in test suites as they may not work correctly with all test frameworks. Consider using a setUp method or factory function instead.

Suggested change

	init() async throws {
	func setUp() async throws {

[Copilot]

The initializer contains a force unwrap (try!) which could cause tests to crash if token creation fails. Consider using proper error handling or making this a throwing initializer.

Suggested change

	init() {
	token = try! Token(id: "TokenId",
	init() throws {
	token = try Token(id: "TokenId",

[Copilot]

[nitpick] The nested try statements make error handling unclear. Consider extracting the data loading to a separate variable for better readability and error handling.