如何在 Node.js 服务器中使用 Jest 解决 UnhandledPromiseRejectionWarning

Question

我的测试正确通过，但我不断收到 UnhandledPromiseRejectionWarning。关于如何解决这个问题有什么想法吗？我尝试了很多解决方案，但似乎都不起作用。

node:32535) UnhandledPromiseRejectionWarning: Error: expect(received).toMatchObject(expected)

Matcher error: received value must be a non-null object

Received has value: undefined (node:32535) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
(node:32535) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

这是我的测试文件：

jest.mock("./http");
const { fetchAllUsersData } = require("./http");

test("Data returned from server should be a list of users ", async () => {
  fetchAllUsersData()
    .catch((errorMessage) => expect(errorMessage).toThrowError(Error))
    .then((usersRetrieved) => {
      let users = usersRetrieved[0];
      let userModel = {
        id: 1,
        first_name: "Peggy",
        last_name: "Poppins",
        email: "mpoppins0@squidoo.com",
        ip_address: "192.54.212.191",
        latitude: 34.003135,
        longitude: -117.7228641222,
      };

      expect(users).toMatchObject(userModel);
    });
});

这是我在模拟文件夹中的文件：

      const fetchAllUsersData = () => {
        return Promise.resolve({
          data: [
            {
              id: 1,
              first_name: "Merry",
              last_name: "Poppins",
              email: "mpoppins0@squidoo.com",
              ip_address: "192.54.212.191",
              latitude: 34.003135,
              longitude: -117.7228641,
            },
            {
              id: 15,
              first_name: "George",
              last_name: "Foreman",
              email: "gforeman@clear.com",
              ip_address: "12.564.124.521",
              latitude: 23.592254,
              longitude: 125.454227,
            },
          ],
        });
      };

      exports.fetchAllUsersData = fetchAllUsersData;

Answer 1

出现此错误的原因是 Promise 没有链接到测试中返回。浮动的 Promise 是一种反模式。async..await允许以比原始承诺所需的更少的纪律来实现这一目标。将原始 Promise 与 一起使用通常没有意义async。此外，在同一个测试中测试成功和失败的请求是没有意义的，预期的响应应该是预先确定的。

expect(errorMessage).toThrowError(Error)errorMessage仅当是同步抛出错误的函数时才有效。fetchAllUsersData如果拒绝对象，它将无法按预期工作errorMessage。

它可能应该在一个测试中：

test("...", async () => {
  const usersRetrieved = await fetchAllUsersData();
  ...
  expect(users).toMatchObject(userModel);
});

在另一个测试中：

test("...", async () => {
  await expect(fetchAllUsersData()).rejects.toThrowError(Error);
});

此外，如果您测试__mock__. 他们应该测试生产代码。