为了测试从Firestore拉出的Swift应用程序，我如何模拟QuerySnapshot？

import XCTest
import Firebase
@testable import YourApp

class YourAppTests: XCTestCase {
    var firestore: Firestore!
    
    override func setUp() {
        super.setUp()
        
        // 创建模拟的Firestore实例
        let settings = FirestoreSettings()
        settings.isPersistenceEnabled = false
        firestore = Firestore.firestore()
        firestore.settings = settings
        
        // 使用模拟的数据填充Firestore实例
        let collection = firestore.collection("yourCollection")
        let document = collection.document("yourDocument")
        document.setData(["key": "value"])
    }
    
    override func tearDown() {
        super.tearDown()
        
        // 清除模拟的数据
        let collection = firestore.collection("yourCollection")
        let document = collection.document("yourDocument")
        document.delete()
    }
    
    func testFetchDataFromFirestore() {
        // 创建模拟的QuerySnapshot对象
        let document = firestore.collection("yourCollection").document("yourDocument")
        let querySnapshot = QuerySnapshotMock(documents: [document])
        
        // 模拟从Firestore拉出的数据
        YourApp.fetchDataFromFirestore(querySnapshot) { result in
            switch result {
            case .success(let data):
                XCTAssertEqual(data["key"] as? String, "value")
            case .failure(let error):
                XCTFail("Error: \(error.localizedDescription)")
            }
        }
    }
}

// 模拟的QuerySnapshot类
class QuerySnapshotMock: QuerySnapshot {
    let documents: [DocumentSnapshot]
    
    init(documents: [DocumentSnapshot]) {
        self.documents = documents
    }
    
    // 实现QuerySnapshot的相关方法
    // ...
}