在 Swift 中对异步函数进行单元测试

问：

我正在尝试在我的 swift 项目中测试异步函数，但我在测试的倒数第二行收到此错误 -> 线程 1：“在已失效的会话中创建的任务”wait(for: [expectation], timeout: 20.0)

我知道 API 可以工作并返回数据，因为它在运行项目和在 Postman 中工作。

这是单元测试

func testRswPrice(){
        //Given (Arrange)
        let fromLat = 26.336502
        let fromLon = -81.439354
        let toLat = 26.533842
        let toLon = -81.759150
        let vm = LocationSearchViewModel()
        
        //When (Act)
        let expectation = self.expectation(description: "Compute Price")
        vm.computePrice(fromLat, fromLon, toLat, toLon){ value in
            expectation.fulfill()
            XCTAssertEqual(value, 8000.0)
        }
        // Wait for the expectation to be fulfilled, or time out after a specified duration
        wait(for: [expectation], timeout: 20.0)
    }

这是 vm 内部的功能

func computePrice(_ fromLat: Double, _ fromLon: Double,_ toLat: Double, _ toLon: Double, completion: @escaping (Double?) -> Void){
        let url = URL(string:"NotShowingMyUrlToStackOverflowButPretendItsHere")!
        var request = URLRequest(url: url)
        request.httpMethod = "POST"
        request.setValue("application/json", forHTTPHeaderField: "Content-Type")
        print("fromLat: \(fromLat)    fromLon: \(fromLon)   toLat: \(toLat)    toLon: \(toLon)")
        let body = [
            "from": [
                "latitude": fromLat,
                "longitude": fromLon
            ],
            "to": [
                "latitude": toLat,
                "longitude": toLon
            ]
        ]
        let jsonData = try? JSONSerialization.data(withJSONObject: body)
        request.httpBody = jsonData
        
        URLSession.shared.dataTask(with: request){ data, response, error in
            guard let data = data, error == nil,
                  (response as? HTTPURLResponse)?.statusCode == 200
            else{
                completion(nil)
                return
            }
            
            //Decode JSON response
            do {
                let decoder = JSONDecoder()
                let response1 = try decoder.decode(PriceResponse.self, from: data)
                DispatchQueue.main.async {
                    completion(response1.price)
                    self.screenDisabled = false
                }
            } catch {
                DispatchQueue.main.async {
                    self.showingInvalidAlert = true
                }
                print("THE ERROR IS \(error.localizedDescription)")
            }
            
        }.resume()
    }