[Docs]: Documentation for setting up TypeScript testing with Babel leads to errors

[rjray]

Page(s)

https://jestjs.io/docs/getting-started#using-typescript

Description

Following the instructions to set up testing of TypeScript code with Babel lead me to the following error message:

  ● Test suite failed to run

    Jest encountered an unexpected token

    Jest failed to parse a file. This happens e.g. when your code or its dependencies use non-standard JavaScript syntax, or when Jest is not configured to support such syntax.

    Out of the box Jest supports Babel, which will be used to transform your files into valid JS based on your Babel configuration.

    By default "node_modules" folder is ignored by transformers.

    Here's what you can do:
     • If you are trying to use ECMAScript Modules, see https://jestjs.io/docs/ecmascript-modules for how to enable it.
     • If you are trying to use TypeScript, see https://jestjs.io/docs/getting-started#using-typescript
     • To have some of your "node_modules" files transformed, you can specify a custom "transformIgnorePatterns" in your config.
     • If you need a custom transformation specify a "transform" option in your config.
     • If you simply want to mock your non-JS modules (e.g. binary assets) you can stub them out with the "moduleNameMapper" config option.

    You'll find more details and examples of these config options in the docs:
    https://jestjs.io/docs/configuration
    For information about custom transformations, see:
    https://jestjs.io/docs/code-transformation

    Details:

    /home/rjray/work/web/smdb/server/src/constants/index.ts:5
    export const ReferenceTypes = {
    ^^^^^^

    SyntaxError: Unexpected token 'export'

My jest.config.js is:

/** @type {import('jest').Config} */
const config = {
  moduleNameMapper: {
    "^(constants|controllers|database|db|models|types|utils)":
      "<rootDir>/src/$1",
  },
  transform: {
    "\\.tsx?$": "babel-jest",
  },
  testEnvironment: "node",
};

export default config;

(Without the moduleNameMapper declaration, none of the local import paths in the TS code resolve.)

babel.config.js is:

module.exports = {
  presets: [
    ["@babel/preset-env", { targets: { node: "current" } }],
    "@babel/preset-typescript",
  ],
};

[rjray]

I created a new branch and tried to follow a blog post that used ts-jest, rather than babel. I installed the necessary packages, and updated my jest.config.ts to be:

/** @type {import('ts-jest').JestConfigWithTsJest} **/
export default {
  moduleNameMapper: {
    "^(constants|controllers|database|db|models|types|utils)":
      "<rootDir>/src/$1",
  },
  preset: "ts-jest",
  testEnvironment: "node",
};

I get the same error message. If I remove the moduleNameMapper, then I get import errors (as before) prior to it reaching the module that is the source of the error. If it helps, I've checkpointed the non-working code in the branch at: https://github.com/rjray/smdb/tree/jest-debugging (if you switch to the main branch, you will get the Babel version but not the actual test case itself).

Everything I can find via searching seems to indicate that the TypeScript code under src is not being transformed.

[github-actions[bot]]

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[reeeeedmil]

Could be because of the typescript 5.6. https://github.com/microsoft/TypeScript/issues/59991