javascript - 开玩笑: How to correctly mock a node module?

我想用Jest模拟React Native中的node_module'React Native Keychain'。

在docs之后，我创建了一个名为__mocks__的文件夹，并在其中创建了一个名为react-native-keychain.js的文件。

这是文件中的代码:

export default jest.mock("react-native-keychain", () => {
  const token = "abcdefghijklmnopqrstuvwxyz0123456789";
  const credentials = {
    username: "session",
    password: token
  };
  return {
    setGenericPassword: jest.fn(
      (username, password) => new Promise((resolve, reject) => resolve(true)) // eslint-disable-line no-unused-vars
    ),
    getGenericPassword: jest.fn(() => new Promise((resolve, reject) => resolve(credentials))), // eslint-disable-line no-unused-vars
    resetGenericPassword: jest.fn(() => new Promise((resolve, reject) => resolve(true))) // eslint-disable-line no-unused-vars
  };
});

然后，我为使用该库的功能编写了测试:

import * as keyChainFunctions from "react-native-keychain";
import { setToken, getToken, clearToken } from "./secureStorage";

const token = "abcdefghijklmnopqrstuvwxyz0123456789";

    describe("set token", () => {
      it("saves the token in the keychain", () => {
        expect.assertions(1);
        return setToken(token).then(res => {
          console.log(res);
          console.log(keyChainFunctions);
          expect(keyChainFunctions.setGenericPassword).toHaveBeenCalledWith("session", token);
        });
      });
    });

问题是，测试失败。我收到错误消息:

 FAIL  app/api/secureStorage/secureStorage.test.js
  set token
    ✕ saves the token in the keychain (42ms)

  ● set token › saves the token in the keychain

    expect(jest.fn())[.not].toHaveBeenCalledWith()

    jest.fn() value must be a mock function or spy.
    Received: undefined

      10 |       console.log(res);
      11 |       console.log(keyChainFunctions);
    > 12 |       expect(keyChainFunctions.setGenericPassword).toHaveBeenCalledWith("session", token);
         |                                                    ^
      13 |     });
      14 |   });
      15 | });

      at app/api/secureStorage/secureStorage.test.js:12:52
      at tryCallOne (node_modules/promise/lib/core.js:37:12)
      at node_modules/promise/lib/core.js:123:15
      at flush (node_modules/asap/raw.js:50:29)
 ● set token › saves the token in the keychain

    expect.assertions(1)

    Expected one assertion to be called but received zero assertion calls.

       6 | describe("set token", () => {
       7 |   it("saves the token in the keychain", () => {
    >  8 |     expect.assertions(1);
         |            ^
       9 |     return setToken(token).then(res => {
      10 |       console.log(res);
      11 |       console.log(keyChainFunctions);

      at Object.<anonymous> (app/api/secureStorage/secureStorage.test.js:8:12)

和console.log()产生:

console.log app/api/secureStorage/secureStorage.test.js:10
    true

  console.log app/api/secureStorage/secureStorage.test.js:11
    { default:
       { addMatchers: [Function: addMatchers],

         advanceTimersByTime: [Function: advanceTimersByTime],
         autoMockOff: [Function: disableAutomock],
         autoMockOn: [Function: enableAutomock],
         clearAllMocks: [Function: clearAllMocks],
         clearAllTimers: [Function: clearAllTimers],
         deepUnmock: [Function: deepUnmock],
         disableAutomock: [Function: disableAutomock],
         doMock: [Function: mock],
         dontMock: [Function: unmock],
         enableAutomock: [Function: enableAutomock],
         fn: [Function: bound fn],
         genMockFromModule: [Function: genMockFromModule],
         isMockFunction: [Function: isMockFunction],
         mock: [Function: mock],
         requireActual: [Function: bound requireModule],
         requireMock: [Function: bound requireMock],
         resetAllMocks: [Function: resetAllMocks],
         resetModuleRegistry: [Function: resetModules],
         resetModules: [Function: resetModules],
         restoreAllMocks: [Function: restoreAllMocks],
         retryTimes: [Function: retryTimes],
         runAllImmediates: [Function: runAllImmediates],
         runAllTicks: [Function: runAllTicks],
         runAllTimers: [Function: runAllTimers],
         runOnlyPendingTimers: [Function: runOnlyPendingTimers],
         runTimersToTime: [Function: runTimersToTime],
         setMock: [Function: setMock],
         setTimeout: [Function: setTimeout],
         spyOn: [Function: bound spyOn],
         unmock: [Function: unmock],
         useFakeTimers: [Function: useFakeTimers],
         useRealTimers: [Function: useRealTimers] } }

这告诉我什么:
1.要么进行模拟工作(因为正确返回了true)，要么从React Native Keychain中调用了实际的setGenericPassword函数。
2.由于某种原因，已定义keychainfunctions，但将其定义为jest.mock对象而不是三个模拟函数。

如果该模拟有效，则感觉1和2相互矛盾。
我究竟做错了什么？为什么此模拟无效？如何解释这些奇怪的console.log()和失败的测试？

Bamse在注释中建议仅导出对象。此替代方法起作用。我仍然会对如何正确地做/我做错了什么感兴趣。

const token = "abcdefghijklmnopqrstuvwxyz0123456789";
const credentials = {
  username: "session",
  password: token
};

export const setGenericPassword = jest.fn(
  (username, password) => new Promise((resolve, reject) => resolve(true)) // eslint-disable-line no-unused-vars
);

export const getGenericPassword = jest.fn(
  () => new Promise((resolve, reject) => resolve(credentials)) // eslint-disable-line no-unused-vars
);

export const resetGenericPassword = jest.fn(() => new Promise((resolve, reject) => resolve(true))); // eslint-disable-line no-unused-vars

最佳答案

您可以尝试在测试中使用jest.createMockFromModule并仅模拟所需的方法。 (以前在26之前的Jest版本中称为genMockFromModule)
希望能帮助到你

关于javascript - 开玩笑: How to correctly mock a node module?，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/51492704/