Compute Application Testing for JavaScript

For those times you want to write JavaScript tests against a Fastly Compute application.

NOTE: Your Compute application can be written in any language/framework. This library allows you to write end-to-end tests against the output of your Compute application.

Start and stop a Fastly Compute application in the local testing environment from your tests and make requests to it.

Use with any test runner and framework.

NOTE: @fastly/compute-testing is provided as a Fastly Labs product. Visit the Fastly Labs site for terms of use.

Requirements

For local testing, Fastly CLI is required.

Note that @fastly/compute-testing makes no assumptions or dictates on the language used to build the Compute application. This framework simply starts/stops the application, and helps your code make HTTP requests to it.

Installation

npm install --save-dev @fastly/compute-testing

Usage

Basic usage

The following is a simple example. It uses Node.js's test runner along with Node.js's assertions, but note that any test framework or assertion library can be used.

In your test (./test.js), you can start and stop a Compute application:

import { describe, it, before, after } from 'node:test';
import assert from 'node:assert';
import path from 'node:path';
import url from 'node:url';

import { ComputeApplication } from '@fastly/compute-testing';

describe('Run local Viceroy', function() {

  // Represents the app running in the local development environment
  const app = new ComputeApplication();

  before(async function() {
    // Start the app
    await app.start({
      // Set 'appRoot' to the directory in which to start the app.  This is usually
      // the directory that contains the 'fastly.toml' file.
      appRoot: '/path/to/approot',
      // Optionally set 'addr', which defaults to 'http://127.0.0.1:7676/', it can be
      // used to start the development environment on a different local address or port.
      // addr: 'http://127.0.0.1:7676/'
    });
  });

  it('Response status code is 200', async function() {
    // Make a fetch request to the app. Returns a Promise that resolves to a Response.
    const response = await app.fetch('/');
    assert.equal(response.status, 200);
  });

  it('Response headers include Content-Type: text/html', async function() {
    const response = await app.fetch('/');
    const contentTypeHeaders =
      (response.headers.get('content-type') ?? '')
      .split(',')
      .map(value => value.trim().split(';')[0]);
    assert.ok(contentTypeHeaders.includes('text/html'));
  });

  it('Response body contains <div>Index</div>', async function() {
    const response = await app.fetch('/');
    const text = await response.text();
    assert.ok(text.includes('<div>Index</div>'));
  });

  after(async function() {
    // Shut down the app
    await app.shutdown();
  });

});

You would run this using Node.js in test mode:

node --test

Using a relative path for appRoot

Often your test suite will live in the same code repository as your Compute application. In this case, you may find it useful to specify a relative path.

For example, if your test file is at <repo>/tests/test.js and your test application's root is at <repo>/app, then you can specify the appRoot at the relative path of ../app as so:

    const __dirname = path.dirname(url.fileURLToPath(import.meta.url));
    await app.start({
      appRoot: path.join(__dirname, '../app'),
    });

appRoot can also be specified as a URL path of a file in your Compute application directory. So, if you're using Node.js 20.7 or newer you can use import.meta.resolve:

    await app.start({
      appRoot: import.meta.resolve('../app/package.json'), // any file in the directory
    });

Custom start script

The following example is for a Compute application that is started using a custom startup command.

import { describe, it, before, after } from 'node:test';
import assert from 'node:assert';
import path from 'node:path';
import url from 'node:url';

import { ComputeApplication } from '@fastly/compute-testing';

describe('Run custom app', function() {

  const app = new ComputeApplication();

  before(async function() {
    this.timeout(30000);
    await app.start({
      // Set 'startCommand' to the command that starts your server.
      startCommand: 'npm run start',
      // Set 'appRoot' to the directory in which to run 'startCommand'.
      appRoot: '/path/to/approot',
    });
  });

  // .. remaining tests

});

Use an running local or remote Compute application

In addition, rather than spawning an instance of an edge application, you can use this library to send requests to a Fastly Compute application that is already running on the local development environment, or running on a remote host.

import { describe, it, before, after } from 'node:test';
import assert from 'node:assert';
import path from 'node:path';
import url from 'node:url';

import { ComputeApplication } from '@fastly/compute-testing';

describe('Use running application', function() {

  const app = new ComputeApplication();

  before(async function() {
    await app.start({
      // Set 'addr' to the hostname and port of the running application.
      // Defaults to 'http://127.0.0.1:7676/'.
      addr: 'https://app.example.com/',
    });
  });
  
  // no shutdown, because you're not actually starting or shutting down an instance.

  // .. remaining tests

});

Usage with other tools

Note that this library is tool- and framework-agnostic, and thus can be used with any testing helper tools. The following example shows usage with JSDOM, a DOM testing library for Node.js.

import { describe, it, before, after } from 'node:test';
import assert from 'node:assert';
import path from 'node:path';
import url from 'node:url';

import { JSDOM } from 'jsdom';
import { ComputeApplication } from '@fastly/compute-testing';

describe('JSDOM testing', function() {

  // ...Start development environment...
  
  it('DOM node with id="foo" contains "bar"', async function() {
    const response = await app.fetch('/');
    const dom = new JSDOM(await response.text(), {url: response.url});
    const element = dom.window.document.getElementById('foo');
    assert.ok(element.textContent === 'bar');
  });

  // ...Shut down development environment...

});

Issues

If you encounter any non-security-related bug or unexpected behavior, please file an issue using the bug report template.

Security issues

Please see our SECURITY.md for guidance on reporting security-related issues.

License

MIT.