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Scaffold your JavaScript projects with tests, lint and release scripts


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Scaffold your JavaScript projects with consistent config for tests, lint, release and CI.

aberlaas is a wrapper around Jest, ESLint, Prettier, etc and their plugins so you only install one package in your devDependencies instead of dozens.

I created this module because I got tired of copy-pasting the same configuration files from project to project. With one meta module to handle all the tooling, I could get started on a new project in minutes instead of hours.

Using aberlaas on every project ensured my linting rules and release process is consistent across my projects. Of course, if you don't like the defaults it's shipped with, you can override them as all configuration files are exposed.


yarn add --dev aberlaas yarn run aberlaas init

This will add aberlaas to your devDependencies and bootstrap your project. Config files for all the tools will be created (.eslintrc.js, jest.config.js, etc) and new yarn run scripts will be added for the most common tasks (lint, test, release, etc).

At that point, you should probably commit all the changes.

(Optional) Setup the external services

yarn run aberlaas setup

This will configure third party services like GitHub and CircleCI to work better with aberlaas.

The following table lists all the scripts added:

yarn run husky:precommitRun before any commit (through Husky)
yarn run testRun tests using Jest
yarn run test:watchRun tests using Jest in watch mode
yarn run ciRun testing and linting in CI
yarn run releaseRelease the module on npm

Testing (with Jest)

aberlaas test to run all the Jest tests in ./lib. You can alter the behavior with the following options:

CLI ArgumentDefault valueDescription
[...]./libFiles and directories to test.
--configjest.config.jsJest config file to use
--watchfalseIf enabled, will listen for changes on files and rerun tests
--failFastfalseIf enabled, will stop as soon as one test fails

Note that you can also pass any other command-line flag and they will be passed directly to Jest under the hood.

Jest is loaded with jest-extended allowing you to use new matchers like .toBeString(), .toStartWith(), etc.

New global variables

testName is available in all tests and contains the name of the current it/test block.

captureOutput allows to swallow any stdout/stderr output for later inspection. Output is stripped of any trailing newlines and ANSI characters.

const actual = await captureOutput(async () => { console.log('foo'); }); // actual.stdout = ['foo']

dedent is included in all tests, so you can write multiline strings without having to break your indentation.

describe('moduleName', () => { describe('methodName', () => { it('should test a multiline string', () => { const input = dedent` Leading and trailing lines will be trimmed, so you can write something like this and have it work as you expect: * how convenient it is * that I can use an indented list - and still have it do the right thing`; // … }); });

Precommit hooks

aberlaas uses husky and lint-staged to make sure all committed code follows your coding standard.

All css, js, json and yml files will be checked for parsing errors (using aberlaas lint internally), and if errors are found it will attempt to automatically fix them. If errors persist, it will prevent the commit and let you know which file contains errors so you can fix them before committing again.

Whenever you commit a .js file that has a test attached (or a test file directly), aberlaas test will be run on those files. If the tests don't pass, your commit will be rejected.

Those two measures ensure that you'll never "break the build", by committing invalid files or code that does not pass the test. If you want to ignore this behavior, you can always add the -n option to your git commit command to skip the hooks.


aberlaas release will release the package to npm. It will update the version in package.json as well as creating the related git tag.

When called without arguments, it will prompt you for the next version to package. If called with an argument, this will be used as the next version number (for example, yarn run release 1.1.3). You can also use SemVer increments (for example, yarn run release minor).

Use --dry-run to start a dry-run. It will simulate a release but won't actually push anything to GitHub or npm.

Continuous Integration

aberlaas ci is triggered by CI Servers (currently only CircleCI is supported), and won't do anything when run locally.

When on a CI server it will first display the current node and yarn version, and then test and lint scripts in that order. It will fail whenever one of them fails, or succeed if they all succeed.

The node and yarn version used both locally and on the CI server will be the same. A .nvmrc file is created when running yarn run aberlaas init that will force local users to use the specified version. The same version is also specified in the Docker image pulled by CircleCI. As for Yarn, a local copy of the whole yarn program is added to the repository when first initializing it, so both locals and CI servers will use it.

By default, tests running on the CI will be parallelized on two CPUs (this is what most free CI tier offer). If you have access to higher end machines, you can update this value by passing the --cpu-count=X flag to your aberlaas ci call.


As an optional feature, you can have aberlaas automatically release a new version of your module from the CI environment when relevant.

The CI will then check all the commits since the last release. If any commit is a feat() it will release a new minor version; it any commit is a fix() it will release a new patch version. For major release, you'll have to do it manually.

This option is not enabled by default. If you need it, you need to follow those steps:

  • Run aberlaas setup --auto-release. It will setup the required ENV variables and ssh keys
  • Update your aberlaas ci script to aberlaas ci --auto-release
  • Uncomment the add_ssh_keys in your .circleci.yml file

File structure

./lib/configs contain the default configuration for all the tools. They are exported by the package and thus can be required in userland.

./templates contains default configurations files copied to userland. Each extends the configuration exported in the previous files. Copying files to userland allows user to change the files if they want to change the behavior.

.eslintrc.js, .stylelintrc.js, jest.config.js and .huskyrc.js are local configuration files for aberlaas itself. They eat their own dog food by referencing the same configs as above.

Where does the name Aberlaas come from?

Aberlaas is the base camp from which all great expedition start in the La Horde du Contrevent book. I felt it's a great name for a bootstrapping kit for modules.

For your convenience, aberlass and aberlas are added as aliases by default.


The complete documentation can be found on https://projects.pixelastic.com/aberlaas/



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