With Jest

grammY Testing is ESM-first. Jest requires extra configuration to handle ESM packages.

Setup

npm install --save-dev jest @types/jest ts-jest grammy-testing grammy

ESM configuration

Jest does not support ESM natively. Use --experimental-vm-modules and configure Jest to transform TypeScript with ts-jest in ESM mode:

// package.json
{
  "scripts": {
    "test": "node --experimental-vm-modules node_modules/.bin/jest"
  },
  "jest": {
    "preset": "ts-jest/presets/default-esm",
    "testEnvironment": "node",
    "moduleNameMapper": {
      "^(\\.{1,2}/.*)\\.js$": "$1"
    },
    "transform": {
      "^.+\\.tsx?$": ["ts-jest", { "useESM": true }]
    }
  }
}

tsconfig.json must target ESM:

{
  "compilerOptions": {
    "module": "ESNext",
    "moduleResolution": "bundler"
  }
}

Writing tests

// bot.spec.ts
import { prepareBot } from 'grammy-testing';

import { createBot } from './bot';

describe('my bot', () => {
  it('replies to /start', async () => {
    const { chats } = await prepareBot(createBot());
    const user = chats.newUser();

    await user.sendCommand('/start');

    expect(user.replies.lastOrThrow().text).toBe('Welcome!');
  });
});

Known caveats

• grammy and grammy-testing are ESM-only. If you use CommonJS Jest without --experimental-vm-modules, tests will fail with ERR_REQUIRE_ESM.
• ts-jest v29+ with useESM: true is required. Older versions may need additional config.
• If you hit issues with deepmerge or other ESM-only transitive deps, add them to transformIgnorePatterns:

  "transformIgnorePatterns": ["node_modules/(?!(grammy|@grammyjs|deepmerge)/)"]

Consider Vitest

Vitest handles ESM out of the box with zero configuration and is faster than Jest for most projects. See With Vitest.