Testing with TypeScript and TS-Jest

Hi there,

I was following the TypeScript and Testing guides but I had to work a lot in order to get the tests run with ts-jest.

Setup

This is my setup:

index.ts defines the handler

import { Request, Response, http } from "@google-cloud/functions-framework";

// Register an HTTP function with the Functions Framework

export async function helloHTTPFunction(req: Request, res: Response) {
  // Your code here

  // Send an HTTP response
  res.send("OK");
}

http("helloHTTPFunction", helloHTTPFunction);

index.test.ts defines the handler's test

import {
  HttpFunction,
  Request,
  Response,
} from "@google-cloud/functions-framework";
// @ts-ignore
import { getFunction } from "@google-cloud/functions-framework/testing";

describe("HelloTests", () => {
  beforeAll(async () => {
    // load the module that defines HelloTests
    await import("./index");
  });

  it("is testable", () => {
    // get the function using the name it was registered with
    const helloHTTPFunction = getFunction(
      "helloHTTPFunction"
    ) as HttpFunction;

    // a Request stub with a simple JSON payload
    const req = {
      body: { foo: "bar" },
    } as Request;
    // a Response stub that captures the sent response
    const res = {
      send: (result) => {
        // assert the response matches the expected value
        expect(result).toBe("OK");
      },
    } as Response;

    // invoke the function
    helloHTTPFunction(req, res);
  });
});

jest.config.ts ts-jest config file

import type { JestConfigWithTsJest } from "ts-jest";

const config: JestConfigWithTsJest = {
  preset: "ts-jest",
  slowTestThreshold: 5000,
  testEnvironment: "node",
  silent: true,
  modulePathIgnorePatterns: ["<rootDir>/dist/", "/node_modules/"],
  testPathIgnorePatterns: [
    "<rootDir>/src/fixtures/",
    "<rootDir>/dist/",
    "/node_modules/",
  ],
  coveragePathIgnorePatterns: [
    "<rootDir>/src/fixtures/",
    "<rootDir>/dist/",
    "/node_modules/",
  ],
};

export default config;

tsconfig.json defines TS settings

{
  "compilerOptions": {
    "target": "ES2020",
     "module": "CommonJS",
     "moduleResolution": "nodenext",
     "outDir": "dist",
     "esModuleInterop": true,
     "strict": true,
     "skipLibCheck": true 
  }
}

Environment

Node 18.12.1
TypeScript 4.9.5
jest 29.4.3
ts-jest 29.0.5
@google-cloud/functions-framework 3.1.3

OS: macOS Ventura on M1 Pro processor

Error

I get this error when I try to import the testing submodule without the // @ts-ignore in the test file

I think it's related to this TypeScript issue and the way the package.json is declared in @google-cloud/functions-framework module.

The test will also fail if not using the --experimental-vm-modules whith jest, but that's because of the await import("./index") statement in the hook.

So you need to add this to the package.json scripts

"test": "NODE_OPTIONS=--experimental-vm-modules jest"

and then launch npm test.

Workaround

Adding the // @ts-ignore does the trick. However, if I am not messing up with the TS settings too much, wouldn't it be nice to have a more TS-friendly testing module package declaration?

And if you think (and I might agree with you) that this issue is more a TS problem than your library's, then could you please extend the documentation by adding a "testing with typescript" section in the docs (feel free to add my workaround if deemed good enough)?

docs/typescript.md と docs/testing-functions.md を読み、次に testing サブモジュールの package export または宣言、およびリポジトリの Jest/TypeScript セットアップを調査します。報告されている ts-jest の import 問題を再現し、NODE_OPTIONS の回避策または確認済みのパッケージ宣言の制限を含む、サポートされている TypeScript テスト設定を文書化します。完了とは、ガイドが実行可能で、例が実行できる状態を意味します。