javascript - React - 在功能组件中测试外部功能

Question

我有一个使用 React Hooks 的功能组件。我有一个更新该组件状态的函数 (evaluateFunction)。

此更新状态函数调用外部函数来检索数据，如下所示:

import { calculatePerformanceTime } from "../../helpers/calculate-performance-time";

const getChallenge = challengeNumber =>
    calculatePerformanceTime(
        require(`../../../challenges/${challengeNumber}.js`)[
            `dcpChallenge${challengeNumber}`
        ],
        challengeNumber
    );

export const TestComponent = _ => {
    const [inputs, setInputs] = useState({});
    const [result, setResult] = useState({});
    const evaluateFunction = value => setResult(getChallenge(value)(inputs));
    return (
        <div>
          <button onClick={() => evaluateFunction(1)} />
        </div>
    );
};

当我模拟点击以测试是否调用了 calculatePerformanceTime 时，它会抛出此错误:

TypeError: getChallenge(...) is not a function

我尝试导出 getChallenge 但没有成功。

我如何测试点击按钮时是否调用了该函数？

这是我到目前为止一直在测试的内容:

import React from "react";
import Adapter from "enzyme-adapter-react-16";
import { configure, shallow } from "enzyme";
import { ChallengeSolution } from "./ChallengeSolution";
import { calculatePerformanceTime } from "../../helpers/calculate-performance-time";
configure({ adapter: new Adapter() });

const mockFunction = jest.fn();
const mockInputData = 1;

jest.mock(`!raw-loader!../../challenges/1.js`, () => "MOCK_RAW", {
    virtual: true
});

jest.mock(`!raw-loader!../../challenges/2.js`, () => "MOCK_RAW", {
    virtual: true
});

jest.mock("../../helpers/calculate-performance-time.js");

describe("ChallengeSolutionComponent", () => {
    let wrapper;
    const tabNumber = 2;
    beforeEach(() => {
        wrapper = shallow(<ChallengeSolution selectedTab={tabNumber} />);
    });

    describe("when component was mount", () => {
        it("should render form correctly", () => {
            const title = wrapper.find(".challenge-solution__title");
            const button = wrapper.find(".challenge-solution__button");
            button.simulate("click");
            expect(calculatePerformanceTime).toHaveBeenCalled();
            expect(title.text()).toEqual(`Daily Coding Solution #${tabNumber}`);
        });
    });
});

Answer 1

这一行:

jest.mock("../../helpers/calculate-performance-time.js");

...将 calculatePerformanceTime 设置为返回 undefined 的空模拟函数。

由于 getChallenge 返回调用 calculatePerformanceTime 的结果，它也返回 undefined。

然后，当这条线运行时:

const evaluateFunction = value => setResult(getChallenge(value)(inputs));

...它尝试将 getChallenge(...) 的结果用作函数并使用 inputs 调用它，但失败了，因为它试图将 undefined 作为函数调用。

---

您需要模拟 calculatePerformanceTime 以返回一个函数:

import React from "react";
import Adapter from "enzyme-adapter-react-16";
import { configure, shallow } from "enzyme";
import { ChallengeSolution } from "./ChallengeSolution";
import * as calculatePerformanceTimeModule from "../../helpers/calculate-performance-time";  // import the module
configure({ adapter: new Adapter() });

const mockFunction = jest.fn();
const mockInputData = 1;

jest.mock(`!raw-loader!../../challenges/1.js`, () => "MOCK_RAW", {
  virtual: true
});

jest.mock(`!raw-loader!../../challenges/2.js`, () => "MOCK_RAW", {
  virtual: true
});

const spy = jest.spyOn(calculatePerformanceTimeModule, 'calculatePerformanceTime');
spy.mockReturnValue(() => { /* this returns a function...fill in the return value here */ });

describe("ChallengeSolutionComponent", () => {
  let wrapper;
  const tabNumber = 2;
  beforeEach(() => {
    wrapper = shallow(<ChallengeSolution selectedTab={tabNumber} />);
  });

  describe("when component was mount", () => {
    it("should render form correctly", () => {
      const title = wrapper.find(".challenge-solution__title");
      const button = wrapper.find(".challenge-solution__button");
      button.simulate("click");
      expect(spy).toHaveBeenCalled();  // Success!
      expect(title.text()).toEqual(`Daily Coding Solution #${tabNumber}`);
    });
  });
});