🐠 🃏 🚀 - Brings tree-shaking to Jest, speeding up your test runs, using Babel
AGPL-3.0 License
babel-jest-boost
figures out the original export of your imported specifiers and rewrites your import statements to bypass barrel files and re-exports. This prevents jest from requiring, compiling and executing irrelevant code, speeding up your test runs.
Assume the following structure:
.
├── lib
│ ├── lib.js # export function libFunc () {}
│ └── index.js # export * from './lib.js'
└── code.js # import { libFunc } from './lib';
Only for the testing transpilation babel-jest-boost
will convert the import statement in code.js
to:
import { libFunc } from '/home/myuser/myproject/lib/lib.js';
It will also replace jest.mock()
function calls in exaclty the same manner.
npm install -D @gtsopanoglou/babel-jest-boost
babel-jest-boost/plugin
You may use babel-jest-boost
as a regular babel plugin. It needs access to your jest config (moduleNameMapper
and modulePaths
in particular). To help you do that we export a jestConfig
object:
+ const { jestConfig } = require("@gtsopanoglou/babel-jest-boost/config");
...
plugins: [
[
+ require.resolve('@gtsopanoglou/babel-jest-boost/plugin'),
+ { jestConfig, /* babel-jest-boost options */ }
]
]
babel-jest-boost/transformer
This option is not recommended yet because it hasn't been tested thoroughly. Use can the pre-made transformer exported from @gtsopanoglou/babel-jest-boost/transformer
which takes care of passing the jestConfig
object for you:
- const babelJest = require("babel-jest").default;
+ const babelJestBoost = require("@gtsopanoglou/babel-jest-boost/transformer");
- module.exports = babelJest.createTransformer({ /* babel config */ });
+ module.exports = babelJestBoost.createTransformer({ /* babel config */ }, { /* babel-jest-boost options */ });
Since babel-jest-boost
modifies the transpiled code, you will need to clear jest's cache before each run (just for this integration phase) to ensure you see non-cached results:
jest --clearCache && jest # or whatever you testing command is
It is likely that some tests will now break. The breakage may be caused by some implicit dependency in your code that you're not aware of, or some bug within babel-jest-boost
.
Either way, you are not going to fix them right now. In order to overcome this problem you have two tools: importIgnorePatterns
plugin option and the no-boost
directive.
Use importIgnorePatterns
to match import statements that cause breakages when by-passed. For instance:
import { port } from 'config';
console.log(port)
Use { importIgnorePatterns: ['config'] }
to prevent babel-jest-boost
from re-writing this import statement.
The no-boost
directive prevent the whole file (either test file or source code) from being parsed and re-written by babel-jest-boost
. For instance:
// @babel-jest-boost no-boost
import { port } from 'config';
console.log(port)
Once your tests are green, you are done. You can now keep running your tests are usual without having to clear your cache.
importIgnorePatterns
[array<string>]
Array of strings/regexes, import paths matching these regexes will prevent babel-jest-boost
from rewritting them. For instance, assuming the example above:
.
├── lib
│ ├── lib.js # export function libFunc () {}
│ └── index.js # export * from './lib.js'
└── code.js # import { libFunc } from './lib';
In this scenario, importIgnorePatterns
will be matched against the only import statement in this tree, import { libFunc } from './lib'
, so if you wish to exclude imports to ./lib
from being re-written, you can use:
{ importIgnorePatterns: ['./lib'] }
This is intended to help you defer refactoring some barrels or modules that are causing trouble or breaking your tests when you integrate this plugin.
ignoreNodeModules
[boolean]
Set this flag to true if you want to completely ignore all node_modules imports from being re-written. Default is false.
no-boost
You can let the plugin know that you do not wish to parse a particular file by adding the following comment anywhere within the file (usually at the top)
// @babel-jest-boost no-boost
import { libFunc } from './lib';
Any import statements within this particular file will not be re-written.
jest.mock
calls are properly treated.babel-jest-boost
and test to measure the performance increase. Do this in the CI/CD pipeline