javascript - 如何访问从模拟库返回的模拟方法

Question

我正在模拟@elastic/elasticsearch库，我想测试是否使用正确的参数调用了search方法，但是在从测试中访问search时遇到了问题。
在我的ES模拟中，我只是导出一个包含Client Prop 的对象，该对象返回另一个具有search Prop 的对象。这是从库访问search的方式

const { Client } = require('@elastic/elasticsearch')
const client = new Client(...)
client.search(...)

__mocks __ / @ elastic / elasticsearch

module.exports = {
    Client: jest.fn().mockImplementation(() => {
        return {
            search: (obj, cb) => {
                return cb(
                    '',
                    {
                        statusCode: 200,
                        body: {
                            hits: {
                                hits: [
                                    {
                                        _source: esIndexes[obj.index]
                                    }
                                ]
                            }
                        }
                    }
                )
            }
        }
    })
}

__tests __ / getAddresses.test.js

const { getAddresses } = require('../src/multiAddressLookup/utils/getAddresses')
const { Client } = require('@elastic/elasticsearch')

beforeEach(() => {
    process.env.ES_CLUSTER_INDEX = 'foo'
    process.env.ui = '*'
})

describe('multiAddressLookup', () => {
    test('Should return the correct premises data with only the relevant "forecasted_outages"', async () => {
        const event = {
            foo: 'bar'
        }
        const esQueryResponse = {
            "body": "\"foo\":\"bar\"",
            "headers": {"Access-Control-Allow-Origin": '*'},
            "statusCode": 200
        }

        await expect(getAddresses(event)).resolves.toEqual(esQueryResponse)
        expect(Client().search).toHaveBeenCalled()  // This fails with 0 calls registered
    })
})

Answer 1

我不确定这种情况的确切文档，但是在查看Jest文档的Jest: The 4 ways to create an ES6 Mock Class - Automatic mock部分时我就知道了。
首先，需要将ES模拟中的search方法__mocks__/@elastic/elasticsearch转换为一个简单的模拟函数jest.fn()。这样做使我们可以访问 Jest 模拟所提供的属性和值。
__mocks__/@elastic/elasticsearch.js 转换

module.exports = {
    Client: jest.fn().mockImplementation(() => {
        return {
            search: jest.fn((obj, cb) => {
                return cb(
                    '',
                    {
                        statusCode: 200,
                        body: {
                            hits: {
                                hits: [
                                    {
                                        _source: esIndexes[obj.index]
                                    }
                                ]
                            }
                        }
                    }
                )
            })
        }
    })
}

其次，在测试中，我们需要遵循 Client模拟类的路径，直到找到方法为止。语法为 MockClass.mock.results[0].value.mockFunction。
示例测试

const { Client } = require('@elastic/elasticsearch')  // This is located in the "__mocks__" folder in the root of your project

const { getAddresses } = require('../../src/getAddresses')  // This is the file we wrote and what we are unit testing

describe('getAddresses', () => {
    it('Should call the ES Search method', async () => {
        const event = { ... }
        const expected = { ... }
        await expect(getAddresses(event)).resolves.toEqual(expected)  // pass
        expect(Client.mock.results[0].value.search).toHaveBeenCalled()  // pass
    })
})