#gist-bookmark #jest #test #esm #alias #js

how-to-jest-esm.md

Jest added to project with aliasing and eslint rules. Jest is not supported esm & esm mocks yet, that's why we are forced to use jest-esm-transformer (Babel transform under the hood test modules & *.spec scripts to CommonJs). Without transform configuration we have error: SyntaxError: Cannot use import statement outside a module.

Nowadays (2022-01-12) we can esm without Babel only by ts-jest?

No! ts-jest uses Babel too and is only needed to catch additional type errors.

Read more:

• Pure ESM package gist
• Setting up Jest with ESM gist
• jest-clean-console-reporter
• awesome-jest#reporters
• ts-jest with old 2019 configuration for ts tested modules & ts tests
• another "boilerplate" ts-jest configuration
• StyleLint trying move to esm (jest too)
• Chromium headless & page model by Playwright ("Автотесты на базе playwright и jest")
• javascript-testing-best-practices
• nodejs-integration-tests-best-practices

100% Func coverage is fixed by migrating from function to Object.

esm for Jest (also with Babel), classic way with @babel/preset-env solve import keyword errors:
package.json > scripts:
"test": "set NODE_ENV=envJest&&node -r esm ./node_modules/jest/bin/jest.js --runInBand --no-cache"

babel.config.json:

{
	"env": {
		"envJest": {
			"presets": ["@babel/preset-env"]
		}
	}
}

My solution with Babel.