如何使用Jest模拟Node.js中的Postgresql(pg)

本文介绍了如何使用Jest模拟Node.js中的Postgresql(pg)的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我是node.js的新手.我正在使用pg和pg-native来为无服务器应用程序在node.js中为postgresql编写代码.我需要为此编写单元测试.我无法使用玩笑或sinon模拟pg客户端.

I am new in node.js. I am writing code in node.js for postgresql using pg and pg-native for serverless app. I need to write unit test for it. I am unable to mock pg client using jest or sinon.

我的实际代码是这样的

const { Client } = require('pg'); export const getAlerts = async (event, context) => { const client = new Client({ user: process.env.DB_USER, host: process.env.DB_HOST, database: process.env.DB_DATABASE, password: process.env.DB_PASSWORD, port: process.env.PORT }); await client.connect(); try { const result = await client.query(`SELECT * FROM public.alerts;`); console.log(result.rows); client.end(); return success({ message: `${result.rowCount} item(s) returned`, data: result.rows, status: true }); } catch (e) { console.error(e.stack); client.end(); return failure({ message: e, status: false }); } };

如何在此处模拟pg客户端?

How to mock pg client here?

推荐答案

以下是使用jestjs的单元测试解决方案:

Here is the unit test solution using jestjs:

index.js:

const { Client } = require('pg'); const { success, failure } = require('./handler'); export const getAlerts = async (event, context) => { const client = new Client({ user: process.env.DB_USER, host: process.env.DB_HOST, database: process.env.DB_DATABASE, password: process.env.DB_PASSWORD, port: process.env.PORT, }); await client.connect(); try { const result = await client.query(`SELECT * FROM public.alerts;`); console.log(result.rows); client.end(); return success({ message: `${result.rowCount} item(s) returned`, data: result.rows, status: true }); } catch (e) { console.error(e.stack); client.end(); return failure({ message: e, status: false }); } };

hander.js:

export function success(data) {} export function failure(data) {}

index.spec.js:

import { getAlerts } from './'; import { Client } from 'pg'; import { success, failure } from './handler'; jest.mock('pg', () => { const mClient = { connect: jest.fn(), query: jest.fn(), end: jest.fn(), }; return { Client: jest.fn(() => mClient) }; }); jest.mock('./handler.js', () => { return { success: jest.fn(), failure: jest.fn(), }; }); describe('59540432', () => { let client; beforeEach(() => { client = new Client(); }); afterEach(() => { jest.clearAllMocks(); }); it('should success', async () => { client.query.mockResolvedValueOnce({ rows: [], rowCount: 0 }); await getAlerts(); expect(client.connect).toBeCalledTimes(1); expect(client.query).toBeCalledWith('SELECT * FROM public.alerts;'); expect(client.end).toBeCalledTimes(1); expect(success).toBeCalledWith({ message: '0 item(s) returned', data: [], status: true }); }); it('should failure', async () => { const mError = new Error('dead lock'); client.query.mockRejectedValueOnce(mError); await getAlerts(); expect(client.connect).toBeCalledTimes(1); expect(client.query).toBeCalledWith('SELECT * FROM public.alerts;'); expect(client.end).toBeCalledTimes(1); expect(failure).toBeCalledWith({ message: mError, status: false }); }); });

单元测试结果覆盖率100％:

Unit test result with 100% coverage:

PASS src/stackoverflow/59540432/index.spec.js (11.792s) 59540432 ✓ should success (16ms) ✓ should failure (5ms) console.log src/stackoverflow/59540432/index.js:3131 [] console.error src/stackoverflow/59540432/index.js:3155 Error: dead lock at /Users/ldu020/workspace/github/mrdulin/jest-codelab/src/stackoverflow/59540432/index.spec.js:39:20 at step (/Users/ldu020/workspace/github/mrdulin/jest-codelab/src/stackoverflow/59540432/index.spec.js:33:23) at Object.next (/Users/ldu020/workspace/github/mrdulin/jest-codelab/src/stackoverflow/59540432/index.spec.js:14:53) at /Users/ldu020/workspace/github/mrdulin/jest-codelab/src/stackoverflow/59540432/index.spec.js:8:71 at new Promise (<anonymous>) at Object.<anonymous>.__awaiter (/Users/ldu020/workspace/github/mrdulin/jest-codelab/src/stackoverflow/59540432/index.spec.js:4:12) at Object.<anonymous> (/Users/ldu020/workspace/github/mrdulin/jest-codelab/src/stackoverflow/59540432/index.spec.js:38:24) at Object.asyncJestTest (/Users/ldu020/workspace/github/mrdulin/jest-codelab/node_modules/jest-jasmine2/build/jasmineAsyncInstall.js:102:37) at resolve (/Users/ldu020/workspace/github/mrdulin/jest-codelab/node_modules/jest-jasmine2/build/queueRunner.js:43:12) at new Promise (<anonymous>) at mapper (/Users/ldu020/workspace/github/mrdulin/jest-codelab/node_modules/jest-jasmine2/build/queueRunner.js:26:19) at promise.then (/Users/ldu020/workspace/github/mrdulin/jest-codelab/node_modules/jest-jasmine2/build/queueRunner.js:73:41) at process._tickCallback (internal/process/next_tick.js:68:7) ----------|----------|----------|----------|----------|-------------------| File | % Stmts | % Branch | % Funcs | % Lines | Uncovered Line #s | ----------|----------|----------|----------|----------|-------------------| All files | 100 | 100 | 100 | 100 | | index.js | 100 | 100 | 100 | 100 | | ----------|----------|----------|----------|----------|-------------------| Test Suites: 1 passed, 1 total Tests: 2 passed, 2 total Snapshots: 0 total Time: 14.109s

源代码: github/mrdulin /jest-codelab/tree/master/src/stackoverflow/59540432