在使用 React Native 和 Hooks 时，状态在 Jest 测试期间没有更新

Question

>我正在尝试测试组件中的功能，基本思想是设置某种状态，当按下按钮时，会调用具有设置状态的函数。代码有效，但是当我尝试测试它时，我没有得到预期的结果，就好像在测试期间从未设置过状态一样。

我正在使用带有钩子的功能组件(useState(在用Jest和Enzyme测试的React Native应用程序中。

复制我的问题的一个例子是：

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();
    const button2 = wrapper.findWhere(node => node.prop("title") === "Button 2")
                        .first();
    button1.props().onPress();
    button2.props().onPress();
    expect(button2Press).toHaveBeenCalledWith("Hello");
  });
});

任何关于我做错/缺失的帮助都会很棒。

Answer 1

这里的问题是两件事。首先我需要调用wrapper.update();执行操作后将导致状态更新。其次，我需要在执行wrapper.update();后再次找到该元素，以使该元素具有更新状态。

工作解决方案是：

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");
  });
});