jest-typescript-seed

If you want to write jest unit tests in typescript without using any of the popular webframeworks like angular or react, then use this project as a seed.

clone this project

git clone git@gitlab.com:frfis/jest-typescript-seed.git

and install the dependencies

npm install

Or follow the steps below to create your own project:

modules you should install

npm install jest ts-jest typescript jest-preset-typescript --save-dev

as described here: https://github.com/DSchau/jest-preset-typescript

add the preset to jest config:

"preset": "jest-preset-typescript"

install the jest type definitions

npm install --save-dev @types/jest

otherwise vscode marks jest functions like test and expect as errors

miscellaneous tips

generate a tsconfig.json with tsc

tsc --init

now its easier to see, which tsc config settings are available.

if you use vscode try vscode-jest extension

https://github.com/jest-community/vscode-jest

You can install vscode extensions without an online connection. Visit the extension page on the marketplace, e.g. https://marketplace.visualstudio.com/items?itemName=Orta.vscode-jest. There is a link Download Extension on the right side under Resources. This downloads a vsix-file. Install it on the command line, e.g.

$ code --install-extension ~/Downloads/Orta.vscode-jest-2.5.8.vsix
Extension 'Orta.vscode-jest-2.5.8.vsix' was successfully installed!

use a separate jest.config.js

do not put all your jest config into package.json

configure outdir in tsconfig.json

{
  "compilerOptions": {
    "target": "es5",
    "module": "commonjs",
    "outDir": "./__TSC_OUT__", // <-- or some other name you like
    "strict": true

}

and add it to ignorepath in jest.config.js

module.exports = {
    preset: "jest-preset-typescript",
    testPathIgnorePatterns: [
        'node_modules',
        '__TSC_OUT__',
    ],
}

dont forget to add node_modules to to ignore path. And add the outdir to .gitignore (Of course alternatively you could also prevent, that jest matches js-files as tests.)

Is this really necessary? No.

If you call tsc directly and you did not configure outdir, the generated js-files might be written to folders where jest looks for test-suite-files. And if you did not change the jest default for matching test file names, jest might find the same suite-file twice, e.g. hello.test.ts and hello.test.js.

https://www.learnrxjs.io

http://rxmarbles.com