react-navigation-hooks：如何测试 useFocusEffect

Question

据我了解，应该这样做，以便 useFocusEffect 可以作为 useEffect 进行测试（模拟）。我使用 useFocusEffect 来获取数据：

useFocusEffect(
  useCallback(() => {
    fetchData();
  }, [fetchData]),
);

错误信息： 反应导航挂钩需要导航上下文，但无法找到。确保您没有忘记创建和渲染反应导航应用程序容器。如果需要访问可选的导航对象，可以使用Context(NavigationContext)，它可能会返回

套餐版本：

"jest": "^24.9.0",
"react-native": "0.61.2",
"react-navigation": "^4.0.10",
"react-navigation-hooks": "^1.1.0",
"@testing-library/react-native": "^4.0.14",

Answer 1

假设您在测试中渲染组件，则需要将其包装在假的

<NavigationContext>

中。这样做可以让

useFocusEffect

查找所需的内容，以确定该组件是否已被应用程序的导航聚焦。

此示例使用

render

中的

react-native-testing-library

。我认为它与其他渲染方法类似。

import { NavigationContext } from "@react-navigation/native"
import { render } from "react-native-testing-library"

// fake NavigationContext value data
const navContext = {
  isFocused: () => true,
  // addListener returns an unscubscribe function.
  addListener: jest.fn(() => jest.fn())
}

// MyComponent needs to be inside an NavigationContext, to allow useFocusEffect to function.
const { toJSON } = render(
  <NavigationContext.Provider value={navContext}>
    <MyComponent />
  </NavigationContext.Provider>
)

Answer 2

这只是@meshantz 的上述答案的完整版本。

import { NavigationContext } from '@react-navigation/native';
import { render } from '@testing-library/react-native';
import React from 'react';

// This would probably be imported from elsewhere...
const ComponentUnderTest = () => {
  useFocusEffect(
    useCallback(() => {
      fetchData();
    }, [fetchData]),
  );
  
  return null;
};

const mockFetchData = jest.fn();
jest.mock('fetchData', () => mockFetchData);

describe('testing useFocusOnEffect in ComponentUnderTest', () => {
  afterAll(() => {
    jest.restoreAllMocks();
  });

  describe('when the view comes into focus', () => {
    it('calls fetchData', () => {
      const navContextValue = {
        isFocused: () => false,
        addListener: jest.fn(() => jest.fn()),
      };

      render(
        <NavigationContext.Provider value={navContextValue}>
          <ComponentUnderTest />
        </NavigationContext.Provider>,
      );

      expect(mockFetchData).toBeCalledTimes(0);

      render(
        <NavigationContext.Provider
          value={{
            ...navContextValue,
            isFocused: () => true,
          }}
        >
          <ComponentUnderTest />
        </NavigationContext.Provider>,
      );

      expect(mockFetchData).toBeCalledTimes(1);
    });
  });
});

Answer 3

对于 TypeScript，也需要满足类型要求，所以在我的例子中，它是通过使用

jest.requireActual

:

来完成的

    const withProvider = (element, store = defaultStore) => {
      // fake NavigationContext value data
      const actualNav = jest.requireActual("@react-navigation/native");
      const navContext = {
        ...actualNav.navigation,
        navigate: () => {},
        dangerouslyGetState: () => {},
        setOptions: () => {},
        addListener: () => () => {},
        isFocused: () => true,
      };
      return (
        <NavigationContext.Provider value={navContext}>
          <MyComponent />
        </NavigationContext.Provider>
      );
    };
    
    it("renders correctly", () => {
      render(withProvider(() => <SportsBooksScreen {...defaultProps} />));
    });

Answer 4

我在这个线程中提出的解决方案存在问题/限制，所以我最终用“React.useEffect”嘲笑“useFocusEffect”。

它做得很好：我的测试现在是绿色的！

jest.mock('@react-navigation/native', () => {
  const { useEffect } = require('react');
  const actualModule = jest.requireActual('@react-navigation/native');

  return {
    ...actualModule,
    useFocusEffect: useEffect,
  };
});

Answer 5

不要使用 useFocusEffect，而是使用 useIsFocused 和 useEffect，并且代码可以正常工作。

In Your component:

import React, { useEffect } from 'react';
import { useIsFocused } from '@react-navigation/native';

const Component = () => {
  const isFocused = useIsFocused();
useEffect(() => {
    if (isFocused) {
      fetchData();
    }
  }, [isFocused]);
  return (<><View testID="child_test_id">{'render child nodes'}</View></>)
}



For Testing:


import Component from '--path-to-component--';
jest.mock('--path-to-fetchData--');
jest.mock('@react-navigation/native', () => {
  return {
    useIsFocused: () => true
  };
});

it('should render child component when available', async () => {
  const mockedData = [];
  fetchData.mockImplementation(() => mockedData);
  let screen = null;
  await act(async () => {
    screen = renderer.create(<Component  />);
  });
  const childNode = screen.root.findByProps({ testID: 'child_test_id' });
  expect(childNode.children).toHaveLength(1);
});

Answer 6

useFocusEffect

使用

navigation.isFocused()

，可从 jest 的

renderHookWithProviders

访问。

做一个

navigation.isFocused.mockReturnValue(true);

应该可以解决问题！现在刚刚尝试了一下，效果很好。

Answer 7

创建组件 FocusEffect

import { useFocusEffect } from "@react-navigation/native";
import { BackHandler } from "react-native";
import React from "react";

export default function FocusEffect({ onFocus, onFocusRemoved }) {
  useFocusEffect(
    React.useCallback(() => {
      onFocus();

      return () => onFocusRemoved();
    }, [onFocus, onFocusRemoved]),
  );
  return null;
}

使用示例：

import React from 'react';
import { Text, View } from 'react-native';
import { FocusEffect } from './components';
    
const App = () => {

onFocus = () => {
   // ============>>>> onFocus <<<<==============
   fetchData();
};

onFocusRemoved = () => {
   // ============>>>> onFocusRemoved <<<<==============
};

return (
    <View>
       <FocusEffect
            onFocus={this.onFocus}
            onFocusRemoved={this.onFocusRemoved}
       />
       <Text>Hello, world!</Text>
   </View>
   )
}
export default App;

Answer 8

如果

useFocusEffect()

中的代码对您的测试并不重要，您可以按如下方式模拟该钩子：

jest.mock("@react-navigation/native", () => ({
  useFocusEffect: jest.fn(),
  // ...
}));