const pg = {} const query = jest.fn(() => ({ rows: [ { a: "string", b: 1, }, ], })) // constructor function Client() {} Client.prototype.query = query Client.prototype.connect = jest.fn() Client.prototype.release = jest.fn() function Pool() {} Pool.prototype.query = query Pool.prototype.connect = jest.fn(() => { return new Client() }) pg.Client = Client pg.Pool = Pool pg.queryMock = query module.exports = pg