玩笑：process.env.PORT的测试问题

Question

编辑：经过一番尝试后，我意识到该问题与过程变量无关，但与出于某种原因我的服务器实例仅执行一次的事实有关。我仍在调查中，我将随时更新该帖子。

我正在尝试获得100％的覆盖率，但我一直无法测试此行：

const port = config.get("port") || process.env.PORT || 3000;

似乎我不能多次设置process.env.PORT。

const config = require("config");

// This checks if a port is being used
function portUsed(port) {
  return new Promise((resolve, reject) => {
    const net = require("net");
    const server = net.createServer();

    server.once("error", err => {
      if (err.code === "EADDRINUSE") {
        resolve(true);
      }
    });

    server.once("listening", () => {
      server.close();
      resolve(false);
    });

    server.listen(port);
  });
}

describe("index", () => {
  // this works
  it("should use process.env.PORT if config.get('port') is not set", async () => {
    config.port = null;
    process.env.PORT = 3333;
    const server = require("../../index");
    const result = await portUsed(3333);
    expect(result).toBe(true);
    await server.close();
  });

  // This does not work, but if you comment out / remove the previous test, it will work!
  it("should default to port 3000 if other variables are not set", async () => {
    config.port = null;
    delete process.env.PORT;
    const server = require("../../index");
    const result = await portUsed(3000);
    expect(result).toBe(true);
    await server.close();
  });

});

基本上，这两个测试之一将运行。我在做什么错？

index.js

const express = require("express");
const app = express();
const config = require("config");

const logger = require("./startup/logging");
require("./startup/console")(app);
require("./startup/database")();
require("./startup/routes")(app);

app.use(express.urlencoded({ extended: true }));

logger.info(config.get("name"));
// delete config.port;
// delete process.env.PORT;
// console.log("config", config.port);
console.log("server", process.env.PORT);
const port = config.get("port") || process.env.PORT || 3000;
const server = app.listen(port, () => logger.info(`Listening on port ${port}.`));

module.exports = server;

Answer 1

我的测试无法正常工作的原因是，所需的模块（require("../../index.js")）将被缓存，因此仅创建了一个服务器实例。要解决这个问题，只需使用：

beforeEach(() => jest.resetModules());