add jest+typescript test

[iambumblehead]

@cyberwombat either "tsm" or "ts-node" could be used the same way here, but this PR uses --loader=tsm now.

re #154

[iambumblehead]

@cyberwombat would this type of test setup work for your tests?

[cyberwombat]

I should be able to use tsm - right now I use ts-jest transform. Ive never used tsm as a loader but happy to experiment.

[iambumblehead]

I did not know about ts-jest transform... I'm interested to change this PR to use the ts-jest transform

[cyberwombat]

Ya my jest.config.ts looks like this:

export default {
  testEnvironment: 'jest-environment-node',
  setupFiles: ['./test/setup.ts'],
  setupFilesAfterEnv: ['./test/bootstrap.ts'],
  transform: {
    '^.+\\.tsx?$': [
      'ts-jest',
      {
        useESM: true,
        diagnostics: false,
        compilerHost: true,
        incremental: true
      }
    ]
  },
  moduleNameMapper: {
    '^(\\.{1,2}/.*)\\.js$': '$1',
    '^lib/(.*)$': 'src/lib/$1',
   ...
  },
  extensionsToTreatAsEsm: ['.ts'],
  testPathIgnorePatterns: ['<rootDir>/dist', '.history'],
  modulePaths: ['<rootDir>/src', '<rootDir>/test', '<rootDir>'],
  preset: 'ts-jest'
}

[iambumblehead]

Actually, based on my admittedly limited understanding of jest... probably jest transform will not work. I think the ts transformation must occur through a --loader like tsm or ts-node. I can try to use the jest.config.ts provided but I don't believe I will succeed.

[cyberwombat]

I am not attached - I do want to be able to use TS files for my setupFiles and setupFilesAfterEnv however as these reference common TS libs in main code. I will try using tsm instead tomorrow and see what happens in general.

[iambumblehead]

jest tries to use ts-node, so updating this PR to use ts-node rather than tsm seems like a good idea.

when using the jest.config.ts, errors like these occur...

Error: Jest: Failed to parse the TypeScript config file /home/bumble/software/esmock/tests/tests-jest-ts/jest.config.ts
  Error: Must use import to load ES Module: /home/bumble/software/esmock/tests/tests-jest-ts/jest.config.ts
require() of ES modules is not supported.
require() of /home/bumble/software/esmock/tests/tests-jest-ts/jest.config.ts from /home/bumble/software/esmock/tests/tests-jest-ts/node_modules/jest-config/build/readConfigFileAndSetRootDir.js is an ES module file as it is a .ts file whose nearest parent package.json contains "type": "module" which defines all .ts files in that package scope as ES modules.
Instead change the requiring code to use import(), or remove "type": "module" from /home/bumble/software/esmock/tests/tests-jest-ts/package.json.

[cyberwombat]

Hmm. I can't tell if its struggling with a TS config or just the ESM. I think the latter. What I did is have "type": "module" in my package.json and use this for my tsconfig.json:

{
  "extends": "@tsconfig/node14/tsconfig.json",
  "compilerOptions": {
    "useUnknownInCatchVariables": false,
    "target": "es2020",
    "lib": ["es2020"],
    "module": "esnext",
    "moduleResolution": "Node",
    "esModuleInterop": true, // Eases ESM support
    "types": ["node"],
    "allowSyntheticDefaultImports": true,
    "declaration": true,
    "strict": true,
    "strictNullChecks": true,
    "alwaysStrict": true,
    "incremental": true,
    "noImplicitReturns": false,
    "noImplicitThis": false,
    "noUnusedLocals": false,
    "noUnusedParameters": false,
    "noEmit": true,
    "noFallthroughCasesInSwitch": false,
    "inlineSourceMap": true,
    "inlineSources": true,
    "experimentalDecorators": true,
    "strictPropertyInitialization": false,
    "resolveJsonModule": true,
    "outDir": "dist",
    "baseUrl": ".",
    "paths": {
  
    },
    "typeRoots": [
      "node_modules/@types",
      "typings"
      //"node_modules/graphql/type/schema.d.ts",
    ],
    "skipLibCheck": true,
    "forceConsistentCasingInFileNames": true
  }
}

[cyberwombat]

Once think I wanted to avoid is doing all imports with 'js' extensions as that makes a total mess for jest/ts-jest. Also I had to play around to have VSCode Inteliisense play nice so these settings are the result of that.

[iambumblehead]

I haven't succeeded in replacing tsm with ts-jest :/

[cyberwombat]

What about ts-node? From reading comments here and there it seems to have a better overall support w Jest and has native esm loader https://www.npmjs.com/package/ts-node

[iambumblehead]

when tsm is replaced with ts-node/esm, this happens when the tests run,

 FAIL  ./esmock.node-jest.test.ts
  ● Test suite failed to run

    thrown: Object {

        "diagnosticCodes": Array [
          2593,
          2304,
        ],
      }

[iambumblehead]

a ts-node/esm test folder with passing esmock tests is here https://github.com/iambumblehead/esmock/tree/master/tests/tests-nodets this error appears to occur specifically in combination with jest

[iambumblehead]

@cyberwombat the ts-node/esm test at this PR is passing. If you have time and would provide the favor of trying to add something like your jest.config.ts file to the PR that would be awesome. If we can support that file, we should include that with the test.

To use the esmock tests, from esmock's root folder npm install && npm run test:install to fetch all dependencies and then from inside tests/test-jest-ts/ run npm test

[iambumblehead]

let's merge this now, in order to update the wiki with links to this test-jest-ts folder. A separate PR could be used for any subsequent changes

[cyberwombat]

I am having no luck w jest-light-runner. I was not able to run directly from repo (too many links/globals I could not match) but have same scenario on my own code.

[iambumblehead]

ok thanks for helping me to this point

[cyberwombat]

Frankly the solution is probably to dump Jest. It's pretty outdated these days and they've expressed a lack of motivation in supporting ESM mocks. I'm exploring vitest to see if that has better options. It supports TS and ESM natively which is nice. Thank you for your effort

[iambumblehead]

I would be interested to know what you think of vitest, as there are many positive reviews