在打字稿中使用 jest 模拟 postgres 数据库连接（Pool，PoolClient，pg）答案

【问题标题】：Mock postgres database connection(Pool, PoolClient, pg) using jest in typescript在打字稿中使用 jest 模拟 postgres 数据库连接（Pool，PoolClient，pg）
【发布时间】：2021-12-16 13:13:57
【问题描述】：

我有一个从 Postgres 数据库中获取值的简单函数。我需要通过模拟数据库来测试该方法。我尝试了提供的各种方法，但都没有奏效。总会出现一些错误。我尝试了以下解决方案：

以下是我的文件。

db.ts

import { Pool } from 'pg'

const pool = new Pool({
    user: `${process.env.POSTGRES_USER}`,
    database: `${process.env.POSTGRES_DB}`,
    password: `${process.env.POSTGRES_PASSWORD}`,
    port: `${process.env.POSTGRES_PORT}`,
    host: `${process.env.POSTGRES_HOST}`,

})
export default pool;

fetch.ts

import pool from "./db";
import {SO} from "./s2l";

    export async function fetch(code: string): Promise<SO[]>{
        let socalls: SO[] =[]
        const sql = 'Select sg.v1,sg.v2,sg.v3,sg.v4 from table1 sg where code = $1 and sg.r_code not in(\'ABC\', \'XYZ\', \'PQR\') order by sg.datetime asc'
        const values = [code]
        const client =  await pool.connect()
        await client.query(sql, values).then(res => {
            const data = res.rows;
            let so
            data.forEach(row => {
                so ={
                service: {
                    code: row["v1"]
                },
                rCode: row["v2"],
                dVo: row["v3"],
                aVo: row["v4"],
            };
            socalls.push(so)
        });
        }).catch(e => console.error(e))
        .then(() => client.release())
        return Promise.all(socalls);
        }

另外，我需要在查询中动态传递列表。

【问题讨论】：

标签： node.js typescript postgresql unit-testing jestjs

【解决方案1】：

以下方法对我有用

fetch.test.ts

import { fetch } from "./fetch";
import pool from "./db";

describe("Test fetch of so calls from database", () => {
  afterAll(() => {
    jest.resetAllMocks();
  });
  it("Happy case", async () => {
    (pool as any).connect = jest.fn().mockReturnThis();
    (pool as any).query = jest.fn().mockReturnThis();
    (pool as any).release = jest.fn().mockReturnThis();
    (pool as any).query.mockResolvedValueOnce({
      rows: [
        {
          v2: "EHRBFK76TGSMD",
          v3: "355GG",
          v4: "355GG",
          v1: "Q923892GT",
        },
      ],
    });
    const result = await fetchSiteCalls("Y2K");
    expect(result).toEqual([
      {
        rCode: "EHRBFK76TGSMD",
        dVo: "355GG",
        aVo: "355GG",
        service: { code: "Q923892GT" },
      },
    ]);
  });
});

【讨论】：