@onerepo/plugin-jest

Jest is a good framework for headless testing with oneRepo. Jest works well with monorepos because it allows a single runner that can use multiple project configurations. Each workspace in your repository can be a Jest project, enabling Jest to determine which tests to run.

The added benefit of Jest is that as you are working, you can run this single command and it will automatically test appropriate files related to your changes across all workspaces. There’s no need to determine which workspaces to run – and can all be done with --watch mode at the same time.

Installation

Section titled Installation

npm

Install via npm

npm install --save-dev @onerepo/plugin-jest

yarn

Install via Yarn

yarn add --dev @onerepo/plugin-jest

pnpm

Install via pnpm

pnpm install --save-dev @onerepo/plugin-jest

Create a root level jest config with the appropriate references to your workspace Jest configs:

jest.config.js

/** @type {import('jest').Config} */
export default {
  projects: ['<rootDir>/apps/*/jest.config.js', '<rootDir>/modules/*/jest.config.js'],
};

Configuration

Section titled Configuration

jest()

Section titled jest()

jest(opts): Plugin

Include the jest plugin in your oneRepo plugin setup:

onerepo.config.ts

import { jest } from '@onerepo/plugin-jest';

export default {
  plugins: [jest()],
};

Parameters

Section titled Parameters

Parameter	Type
opts	Options

Options

Section titled Options

type Options: {
  config: string;
  name: string | string[];
  passWithNoTests: boolean;
};

Options for configuring the Jest plugin for oneRepo.

onerepo.config.js

export default {
  plugins: [
    jest({
      // optional configuration
    }),
  ],
});

• Default: {}

Type declaration

Section titled Type declaration

config?

Section titled config?

optional config: string;

Specify the main Jest configuration file, if different from <repo>/jest.config.js. This can be relative to the repository root.

onerepo.config.js

export default {
  plugins: [
    jest({
      config: 'configs/jest.config.js'
    }),
  ],
});

name?

Section titled name?

optional name: string | string[];

• Default: 'jest'

Rename the default command name. This configuration is recommended, but not provided, to avoid potential conflicts with other commands.

onerepo.config.js

export default {
  plugins: [
    jest({
      name: ['test', 'jest']
    }),
  ],
});

passWithNoTests?

Section titled passWithNoTests?

optional passWithNoTests: boolean;

• Default: true

Automatically include Jests’s flag --passWithNoTests when running.

onerepo.config.js

export default {
  plugins: [
    jest({
      passWithNoTests: false,
    }),
  ],
});

Recommended tasks

Section titled Recommended tasks

./onerepo.config.ts

import type { Config } from 'onerepo';

export default {
  tasks: {
    'pre-commit': {
      serial: ['$0 jest'],
    },
    'pre-merge': {
      serial: ['$0 jest -a'],
    },
  },
} satisfies Config;

Commands

Section titled Commands

one jest

Section titled one jest

Aliases: one test

Run tests using Jest.

one jest [options...] -- [passthrough]
one jest [options...]

This test commad will automatically attempt to run only the test files related to the changes in your working state. If you have un-committed changes, only those related to files that are in a modified state will be run. If there are no un-committed changes, test files related to those modified since your git merge-base will be run. By passing specific filepaths as extra passthrough arguments an argument separator (two dasshes --), you can further restrict the tests to those files and paths.

Additionally, any other Jest CLI options can be passed as passthrough arguments as well after an argument separator (two dashes --)

Option	Type	Description
--affected	boolean	Select all affected Workspaces. If no other inputs are chosen, this will default to true.
--all, -a	boolean	Run across all Workspaces
--inspect	boolean	Break for the the Node inspector to debug tests.
--pretty	boolean, default: true	Control Jest’s --colors flag.
--staged	boolean	Use files on the git stage to calculate affected files or Workspaces. When unset or --no-staged, changes will be calculated from the entire branch, since its fork point.
--watch	boolean	Shortcut for jest --watch mode.
--workspaces, -w	array	List of Workspace names to run against

Advanced options

Option	Type	Description
--config	string, default: "./jest.config.js"	Path to the jest.config file, relative to the repo root.
--from-ref	string	Git ref to start looking for affected files or Workspaces
--passWithNoTests	boolean, default: true	Allows the test suite to pass when no files are found. See plugin configuration to disable.
--show-advanced	boolean	Pair with --help to show advanced options.
--through-ref	string	Git ref to start looking for affected files or Workspaces

Run only tests related to modified files.

one jest ,test

Runs jest in —watch mode against the currently affected files.

one jest ,test --watch

Run Jest in watch mode against a particular file.

one jest ,test --watch -- path/to/test.ts

Pass any other Jest CLI options after the argument separator.

one jest ,test -- --runInBand --detectOpenHandles