在使用React Native和Hooks的Jest测试期间状态没有更新

问题描述

我正在尝试测试组件中的功能，基本思想是设置了某种状态，并且当按下按钮时，会以设置状态调用一个函数.该代码有效，但是当我尝试对此进行测试时，却没有得到预期的结果，就像在测试期间从未设置状态一样.

I am trying to test functionality in my component, the basic idea is some state is set and when a button is pressed a function is called with the set state. The code works but when I try to test this I don't get the expected result, it is as if the state never gets set during the test.

我正在用Jest和Enzyme测试过的React Native应用程序中使用带有钩子(useState)的功能组件.

I am using a functional component with hooks (useState) in a React Native app tested with Jest and Enzyme.

一个重复我的问题的例子是:

An example which replicates my problem is:

import React, { useState } from "react";
import { View, Button } from "react-native";
import { shallow } from "enzyme";

const Example = function({ button2Press }) {
const [name, setName] = useState("");

  return (
    <View>
      <Button title="Button 1" onPress={() => setName("Hello")} />
      <Button title="Button 2" onPress={() => button2Press(name)} />
    </View>
  );
};

describe("Example", () => {
  it("updates the state", () => {
    const button2Press = jest.fn();
    const wrapper = shallow(<Example button2Press={button2Press} />)
    const button1 = wrapper.findWhere(node => node.prop("title") === "Button 1")
                        .first();
    const button2 = wrapper.findWhere(node => node.prop("title") === "Button 2")
                        .first();

    button1.props().onPress();
    button2.props().onPress();

    expect(button2Press).toHaveBeenCalledWith("Hello");
  });
});

任何对我做错事/失踪的帮助都是很好的.

Any help on what I am doing wrong/missing would be great.

推荐答案

这里的问题是两件事.首先，在执行操作将导致状态更新后，我需要调用 wrapper.update(); .其次，我需要在执行 wrapper.update(); 后再次查找该元素，以使该元素具有更新的状态.

The problem here is 2 things. First I need to call wrapper.update(); after performing actions will cause the state to update. Second I need to find the element again after performing wrapper.update(); for that element to have the updated state.

有效的解决方案是:

import React, { useState } from "react";
import { View, Button } from "react-native";
import { shallow } from "enzyme";

const Example = function({ button2Press }) {
const [name, setName] = useState("");

  return (
    <View>
      <Button title="Button 1" onPress={() => setName("Hello")} />
      <Button title="Button 2" onPress={() => button2Press(name)} />
    </View>
  );
};

describe("Example", () => {
  it("updates the state", () => {
    const button2Press = jest.fn();
    const wrapper = shallow(<Example button2Press={button2Press} />)
    const button1 = wrapper.findWhere(node => node.prop("title") === "Button 1")
                        .first();
    button1.props().onPress();
    wrapper.update(); // <-- Make sure to update after changing the state

    const button2 = wrapper.findWhere(node => node.prop("title") === "Button 2")
                        .first(); // <-- Find the next element again after performing update
    button2.props().onPress();

    expect(button2Press).toHaveBeenCalledWith("Hello");
  });
});

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