jest-nock-fixtures

jest-nock-fixtures is a wrapper for a jest testing environment. It uses nock to record and playback requests during test runs. It is heavily inspired by https://github.com/nock/nock#nock-back

Install

npm install @nerdwallet/jest-nock-fixtures

Setup and usage

Configure jest to setup this wrapper before the tests in each test file are executed. In jest@24, this can be achieved by configuring setupFilesAfterEnv (https://jestjs.io/docs/en/configuration#setupfilesafterenv-array)

---

Create a file to import and activate @nerdwallet/jest-nock-fixtures, in this example named setupAfterEvvJestNockFixtures.js

activating the test wrapper

1/* setupAfterEvvJestNockFixtures.js */
2
3const createJestNockFixturesTestWrapper = require('@nerdwallet/jest-nock-fixtures');
4
5createJestNockFixturesTestWrapper();

optionally, the error message that is thrown in lockdown mode can be configured. This allows you to hint at ways to fix that might be specific to the repo @nerdwallet/jest-nock-fixtures is used in, ex:

1/* setupAfterEvvJestNockFixtures.js */
2
3const createJestNockFixturesTestWrapper = require('@nerdwallet/jest-nock-fixtures');
4
5createJestNockFixturesTestWrapper({
6  unmatchedErrorMessage: (reqs, { fixtureFilepath }) =>
7    `unmatched requests not allowed (found ${
8      reqs.length
9    }).\n\nRun \`npm run test:record\` to update fixtures, and try again.`
10});

Configure Jest

then configure jest to activate @nerdwallet/jest-nock-fixtures and wrap each test file in nock fixture recording behavior

1// in jest config
2{
3  // ... the rest of the jest config
4
5  // run the setup file created in the examples above
6  setupFilesAfterEnv: ['<rootDir>/setupAfterEvvJestNockFixtures.js'],
7  // ignore the folder where the fixtures are saved
8  // so they don't endlessly trigger re-runs in record mode
9  watchPathIgnorePatterns: ['__nocks__'],
10  // add the watch plugin to change modes while in --watch mode
11  // press 'r' to cycle through jest modes between runs
12  watchPlugins: ['@nerdwallet/jest-nock-fixtures/JestWatchPlugin']
13}

Modes

Available modes:

• dryrun: The default, use recorded nocks, allow new http calls, doesn't record anything, useful for writing new tests
• record: record new nocks
• lockdown: use recorded nocks, disables all http calls even when not nocked, doesn't record
• wild: all requests go out to the internet, don't replay anything, don't record anything

@nerdwallet/jest-nock-fixtures reads process.env.JEST_NOCK_FIXTURES_MODE to control its behavior, allowing script aliases to be created, for example:

1  "scripts": {
2    "jest": "jest --coverage",
3    "test": "npm run jest --",
4    "test:wild": "JEST_NOCK_FIXTURES_MODE=wild npm run test --",
5    "test:record": "JEST_NOCK_FIXTURES_MODE=record npm run test --",
6    "test:lockdown": "JEST_NOCK_FIXTURES_MODE=lockdown npm run test --"
7  },

lockdown mode is always used in CI environments (e.g. process.env.CI === true).

An example workflow:

1. develop some code and write some tests. code in question makes external network requests
2. record all the requests that happen during local test runs
3. playback those recordings during CI test runs to ensure consistency

1# while developing
2npm run test -- --watch
3# when ready to push
4npm run test:record
5# commit and push the added/changed `__nocks__/*.json` fixture files
6
7# and then in CI enjoy peace of mind for consistent and reproducable test runs in the context of network requests

Log levels

By default, minimal logs will be printed. To increase the verbosity of the logs, set JEST_NOCK_FIXTURES_VERBOSE when running tests. For example:

1JEST_NOCK_FIXTURES_VERBOSE=1 npm run test

Developing

Main commands:

• yarn install: Install all dependencies
• yarn test: Run unit tests and generate coverage reports

Other commands you might care about:

• yarn lint: Run lint
• yarn format: Automatically fix code issues

Releasing a new version

1. Update the version in package.json. Take care to follow semantic versioning.
2. Update CHANGELOG.md to reflect the changes in the new version.
3. Push both of the above changes to the master branch.
4. Create a new release in the GitHub CI. GitHub Actions will automatically publish the new version to npm.