如何对UIApplication扩展进行单元测试

// UIApplication+Network.swift
import UIKit

extension UIApplication {
    func sendNetworkRequest(url: URL, completion: @escaping (Data?, URLResponse?, Error?) -> Void) {
        let task = URLSession.shared.dataTask(with: url) { data, response, error in
            completion(data, response, error)
        }
        task.resume()
    }
}

// NetworkService.swift
import Foundation

protocol NetworkServiceProtocol {
    func sendRequest(url: URL, completion: @escaping (Data?, URLResponse?, Error?) -> Void)
}

class NetworkService: NetworkServiceProtocol {
    func sendRequest(url: URL, completion: @escaping (Data?, URLResponse?, Error?) -> Void) {
        let task = URLSession.shared.dataTask(with: url) { data, response, error in
            completion(data, response, error)
        }
        task.resume()
    }
}

// UIApplication+Network.swift
import UIKit

extension UIApplication {
    var networkService: NetworkServiceProtocol {
        return NetworkService()
    }

    func sendNetworkRequest(url: URL, completion: @escaping (Data?, URLResponse?, Error?) -> Void) {
        networkService.sendRequest(url: url, completion: completion)
    }
}

// UIApplication+NetworkTests.swift
import XCTest
@testable import YourApp

class UIApplication_NetworkTests: XCTestCase {
    func testSendNetworkRequest() {
        let mockNetworkService = MockNetworkService()
        UIApplication.shared.networkService = mockNetworkService

        let testURL = URL(string: "https://example.com")!
        var receivedData: Data?
        var receivedResponse: URLResponse?
        var receivedError: Error?

        UIApplication.shared.sendNetworkRequest(url: testURL) { data, response, error in
            receivedData = data
            receivedResponse = response
            receivedError = error
        }

        // 等待异步操作完成
        let expectation = XCTestExpectation(description: "Network request completed")
        DispatchQueue.main.asyncAfter(deadline: .now() + 5) {
            expectation.fulfill()
        }
        wait(for: [expectation], timeout: 10)

        // 断言
        XCTAssertNotNil(receivedData)
        XCTAssertNotNil(receivedResponse)
        XCTAssertNil(receivedError)
    }
}

class MockNetworkService: NetworkServiceProtocol {
    func sendRequest(url: URL, completion: @escaping (Data?, URLResponse?, Error?) -> Void) {
        let data = "Mock data".data(using: .utf8)!
        let response = HTTPURLResponse(url: url, statusCode: 200, httpVersion: nil, headerFields: nil)!
        completion(data, response, nil)
    }
}