server-listening

Simple promise to wait for server ready or DOM ready inside a mocha specification

server-listening is a lightweight helper utility to reduce the amount of boilerplate code needed to startup servers when running mocha specifications.

A) Setup

Install package:

$ npm install --save-dev server-listening

Import package:

import { serverListening } from 'server-listening';

B) Usage

Three primary tools:

• serverListening.ready(server) Waits for your node server application to start up
• serverListening.startWebServer(options) Starts and waits for static web server (express), see: start-web-server.spec.js
• serverListening.loadWebPage(url, options) Uses JSDOM to load and wait for a web page, see: load-web-page.spec.js

(for similar functionality using Puppeteer instead, see the puppeteer-browser-ready project).

1. Mocha specification file

import { server } from '../server.js';
before(() => serverListening.ready(server));
after(() =>  serverListening.close(server));

Example usage:
hello-world/mocha.spec.js

NOTE:
Mocha's default timeout is 2,000 milliseconds which often is not enough time for a node server to shutdown.  Use the --timeout flag to help avoid this problem:

"scripts": {
   "test": "mocha *.spec.js --timeout 7000"
}

2. setPort() options

The setPort(options) function is just a handy way to set the environment variable for the HTTP port.  This function is for convenience and is not required.

serverListening.setPort({ port: 9000 });

Option	Meaning	Default
port	Port number for server (0 means choose an unused port).	0
name	Environment variable name to store port number.	'port'

3. Leveraging promises

The ready(server) and close(server) functions return a promise, enabling chaining of operations.

For example, a port variable could be set after the server is ready using:

let port;
before(() => serverListening.ready(server).then(() => port = server.address().port));

4. Example for serverListening.loadWebPage(url)

// Mocha Specification Suite

// Imports
import { assertDeepStrictEqual } from 'assert-deep-strict-equal';
import { serverListening } from 'server-listening';

// Setup
const url = 'https://pretty-print-json.js.org/';
let web;  //fields: url, dom, window, document, title, html, verbose
const loadWebPage =  () => serverListening.loadWebPage(url).then(webInst => web = webInst);
const closeWebPage = () => serverListening.closeWebPage(web);

////////////////////////////////////////////////////////////////////////////////
describe('The web page', () => {
   const getTags = (elems) => [...elems].map(elem => elem.nodeName.toLowerCase());
   before(loadWebPage);
   after(closeWebPage);

   it('has the correct URL', () => {
      const actual =   { url: web.window.location.href };
      const expected = { url: url };
      assertDeepStrictEqual(actual, expected);
      });

   it('body has exactly one header, main, and footer', () => {
      const actual =   getTags(web.document.querySelectorAll('body >*'));
      const expected = ['header', 'main', 'footer'];
      assertDeepStrictEqual(actual, expected);
      });

   });

////////////////////////////////////////////////////////////////////////////////
describe('The document content', () => {
   before(loadWebPage);
   after(closeWebPage);

   it('has a 🚀 traveling to 🪐!', () => {
      const html =     web.document.body.outerHTML;
      const actual =   { '🚀': !!html.match(/🚀/g), '🪐': !!html.match(/🪐/g) };
      const expected = { '🚀': true,                '🪐': true };
      assertDeepStrictEqual(actual, expected);
      });

   });

Above mocha test will output:

  The web page
    ✓ has the correct URL -> https://pretty-print-json.js.org/
    ✓ body has exactly one header, main, and footer

  The document content
    ✓ has a 🚀 traveling to 🪐!

Example of loading a web page into jsdom from a local node server:
https://github.com/dna-engine/data-dashboard/blob/main/spec/spec.js

5. TypeScript declarations

See the TypeScript declarations at the top of the server-listening.ts file.

The declarations provide type information about the API, such as the options for calling serverListening.setPort():

type ServerListeningOptions = {
   port?:  number,  //0 = find unused port
   name?:  string,  //environment variable to pass port number
   };

C) Hello World Example

To try out server-listening locally, enter the following terminal commands:

$ git clone https://github.com/center-key/server-listening.git
$ cd server-listening/hello-world
$ npm install
$ npm test

You can also run the server locally:

$ npm start

and then use a browser to view the 'Hello, World!' message at: http://localhost:3300

---

server-listening is open source under the MIT License.