如何模拟在使用Jest测试的React组件中进行的API调用

Question

我正在尝试模拟将数据检索到组件的fetch（）。

我正在使用它作为模拟提取的模型，但是我无法使其正常工作。

运行测试时出现此错误： babel-plugin-jest-hoist: The module factory of 'jest.mock()' is not allowed to reference any out-of-scope variables.

有没有办法让这些函数返回模拟数据，而不是实际尝试进行真正的API调用？

码

utils / getUsers.js

返回角色映射到每个用户的用户。

const getUsersWithRoles = rolesList =>
  fetch(`/users`, {
    credentials: "include"
  }).then(response =>
    response.json().then(d => {
      const newUsersWithRoles = d.result.map(user => ({
        ...user,
        roles: rolesList.filter(role => user.roles.indexOf(role.iden) !== -1)
      }));
      return newUsersWithRoles;
    })
  );

组件/UserTable.js

const UserTable = () => {
  const [users, setUsers] = useState([]);
  useEffect(() => {
    getTableData();
  }, []);

  const getTableData = () => {
    new Promise((res, rej) => res(getRoles()))
      .then(roles => getUsersWithRoles(roles))
      .then(users => {
        setUsers(users);
      });
  };
  return (...)
};

组件/ 测试 /UserTable.test.js

import "jest-dom/extend-expect";
import React from "react";
import { render } from "react-testing-library";
import UserTable from "../UserTable";
import { getRoles as mockGetRoles } from "../utils/roleUtils";
import { getUsersWithRoles as mockGetUsersWithRoles } from "../utils/userUtils";

const users = [
  {
    name: "Benglish",
    iden: "63fea823365f1c81fad234abdf5a1f43",
    roles: ["eaac4d45c3c41f449cf7c94622afacbc"]
  }
];

const roles = [
  {
    iden: "b70e1fa11ae089b74731a628f2a9b126",
    name: "senior dev"
  },
  {
    iden: "eaac4d45c3c41f449cf7c94622afacbc",
    name: "dev"
  }
];

const usersWithRoles = [
  {
    name: "Benglish",
    iden: "63fea823365f1c81fad234abdf5a1f43",
    roles: [
      {
        iden: "eaac4d45c3c41f449cf7c94622afacbc",
        name: "dev"
      }
    ]
  }
];

jest.mock("../utils/userUtils", () => ({
  getUsers: jest.fn(() => Promise.resolve(users))
}));
jest.mock("../utils/roleUtils", () => ({
  getRolesWithUsers: jest.fn(() => Promise.resolve(usersWithRoles)),
  getRoles: jest.fn(() => Promise.resolve(roles))
}));

test("<UserTable/> show users", () => {
  const { queryByText } = render(<UserTable />);

  expect(queryByText("Billy")).toBeTruthy();
});

Answer 1

默认情况下，jest.mock呼叫由babel-jest...挂起

...这意味着它们在测试文件中的任何其他内容之前运行，因此测试文件中声明的任何变量都不会在范围内。

这就是为什么传递给的模块工厂jest.mock不能引用自身之外的任何东西。

一种选择是像这样在模块工厂内移动数据：

jest.mock("../utils/userUtils", () => {
  const users = [ /* mock users data */ ];
  return {
    getUsers: jest.fn(() => Promise.resolve(users))
  };
});
jest.mock("../utils/roleUtils", () => {
  const roles = [ /* mock roles data */ ];
  const usersWithRoles = [ /* mock usersWithRoles data */ ];
  return {
    getRolesWithUsers: jest.fn(() => Promise.resolve(usersWithRoles)),
    getRoles: jest.fn(() => Promise.resolve(roles))
  };
});

另一种选择是使用jest.spyOn以下方法模拟函数：

import * as userUtils from '../utils/userUtils';
import * as roleUtils from '../utils/roleUtils';

const users = [ /* mock users data */ ];
const roles = [ /* mock roles data */ ];
const usersWithRoles = [ /* mock usersWithRoles data */ ];

const mockGetUsers = jest.spyOn(userUtils, 'getUsers');
mockGetUsers.mockResolvedValue(users);

const mockGetRolesWithUsers = jest.spyOn(roleUtils, 'getRolesWithUsers');
mockGetRolesWithUsers.mockResolvedValue(usersWithRoles);

const mockGetRoles = jest.spyOn(roleUtils, 'getRoles');
mockGetRoles.mockResolvedValue(roles);

另一种选择是自动模拟模块：

import * as userUtils from '../utils/userUtils';
import * as roleUtils from '../utils/roleUtils';

jest.mock('../utils/userUtils');
jest.mock('../utils/roleUtils');

const users = [ /* mock users data */ ];
const roles = [ /* mock roles data */ ];
const usersWithRoles = [ /* mock usersWithRoles data */ ];

userUtils.getUsers.mockResolvedValue(users);
roleUtils.getRolesWithUsers.mockResolvedValue(usersWithRoles);
roleUtils.getRoles.mockResolvedValue(roles);

...并将模拟的响应添加到空的模拟函数中。

Answer 2

不要嘲笑进行 API 调用的工具；存根服务器响应。以下是我如何使用名为nock的 HTTP 拦截器重写您的测试。

import "jest-dom/extend-expect";
import React from "react";
import { render, waitFor } from "react-testing-library";
import UserTable from "../UserTable";

const users = [
  {
    name: "Benglish",
    iden: "63fea823365f1c81fad234abdf5a1f43",
    roles: ["eaac4d45c3c41f449cf7c94622afacbc"]
  }
];

const roles = [
  {
    iden: "b70e1fa11ae089b74731a628f2a9b126",
    name: "senior dev"
  },
  {
    iden: "eaac4d45c3c41f449cf7c94622afacbc",
    name: "dev"
  }
];

const usersWithRoles = [
  {
    name: "Benglish",
    iden: "63fea823365f1c81fad234abdf5a1f43",
    roles: [
      {
        iden: "eaac4d45c3c41f449cf7c94622afacbc",
        name: "dev"
      }
    ]
  }
];

describe("<UserTable/>", () => {
  it("shows users", async () => { // <-- Async to let nock kick over resolved promise
    nock(`${server}`)
      .get('/users')
      .reply(200, {
        data: users
      })
      .get('/usersWithRoles')
      .reply(200, {
        data: usersWithRoles
      })
      .get('/roles')
      .reply(200, {
        data: roles
      });
    const { queryByText } = render(<UserTable />);

    await waitFor(() => expect(queryByText("Billy")).toBeTruthy()); // <-- Is this supposed to be "Benglish"?
  });
});

现在，您的测试套件不知道您如何获取数据，并且您不必维护复杂的模拟。查看进行 API 调用的测试组件以进行更深入的研究。