setup-polly-jest

Overview

This helper provides a convenient way to use PollyJS (HTTP recording, replaying and stubbing tool) in your Jest/Jasmine tests.

Installation

This library has a peer dependency on @pollyjs/core. That means that you will need to install it separately if you don't have it installed yet.

npm install --save-dev setup-polly-jest @pollyjs/core

Usage

This helper behaves almost the same way as built-in Mocha or QUnit helpers for PollyJS. If you used them before, this API should be familiar to you:

/** @jest-environment setup-polly-jest/jest-environment-node */

import { setupPolly } from 'setup-polly-jest';

describe('google.com', () => {
  let context = setupPolly({
    /* default configuration options */
  });

  test('should be able to search', async () => {
    /**
     * The `setupPolly` test helper creates a new polly instance which you can
     * access via `context.polly`. The recording name is generated based on
     * the suite (module) and spec (test) names.
     */
    context.polly.configure({ recordIfMissing: true });

    /* start: pseudo test code */
    await visit('/');
    await fillIn('#search', 'Awesome HTTP stubbing');
    await submit();

    expect(document.getElementById('search-result').textContent).toBe(
      'PollyJS'
    );
    /* end: pseudo test code */

    /**
     * The setupPolly test helper will call `context.polly.stop()` when your test
     * has finished.
     */
  });
});

To learn more about how to use PollyJS or what can you do with polly instance, please refer to PollyJS docs.

For real-world examples, check out "Jest + Node Fetch" or "Jest + Puppeteer" examples in PollyJS docs or tests in this repo.

Supported Test Runners

This library supports jasmine, jest-jasmine2 (default in jest <= 26), and jest-circus (default in jest >= 27) test runners. If you are using setup-polly-jest with jest-circus runner you need to specify custom test environment, either in the test file where you are planning to use setupPolly:

/** @jest-environment setup-polly-jest/jest-environment-node */

const context = setupPolly(/* ... */);

Or configure it for all your tests with testEnvironment config option

// jest.config.js
module.exports = {
  testEnvironment: 'setup-polly-jest/jest-environment-jsdom'
};

Both node and jsdom environments are provided by this library and can be safely used as a replacement for original jest-environment-* environments.

Test Hook Ordering

Accessing context.polly during a test run before the instance of Polly has been created or after it was cleaned up produces the following error:

!> You are trying to access an instance of Polly that is not yet available.

If you need to do some work before the test run, you can access the instance of Polly in beforeEach hook. If you need to do some work before the instance of Polly gets cleaned up and removed, you can do so in afterEach hook.

describe('test', () => {
  const context = setupPolly();

  beforeEach(() => {
    context.polly.server
      .get('/ping')
      .intercept((req, res) => res.sendStatus(200));
  });

  it('does a thing', async () => {
    expect(await fetch('/ping').status).toBe(200);
  });

  afterEach(() => context.polly.flush());
});

Caveats

Although this library is thoroughly covered with unit and intergration tests, its implementation in jasmine environment depends upon overwriting Jasmine methods directly. That means that some major changes in how Jest or Jasmine run tests can lead to this library not working properly anymore.

Contributing

If you stumbled upon any bugs 🐞, have a feature 🚀 in mind or you think that documentation 📝 is lacking in any way, please, feel free to open an issue or submit a pull-request.

LICENCE

ISC