Can Vitest run Jest test files without modifying code?

Yes! By adding `test: { globals: true }` in `vitest.config.ts`, global `describe`, `it`, and `expect` remain globally available.

Jest → VitestAutomated Breaking Change Check

Migrate Jest Unit Tests to Vitest

Convert Jest test suites, configs, and mocks to Vitest. Share identical Vite configurations and execute tests 4x faster with ESM native workers.

From: Jest

→

To: Vitest

Source (Jest)

495 chars

Migrated Target (Vitest)

1ms540 chars

import { describe, it, expect, vi } from 'vitest';
import { UserService } from './user-service';

describe('UserService', () => {
  beforeEach(() => {
    vi.clearAllMocks();
  });

  it('fetches user details and formats response', async () => {
    const mockFetch = vi.fn().mockResolvedValue({ id: '1', name: 'DevFlow' });
    vi.spyOn(global, 'fetch').mockImplementation(mockFetch as any);

    const user = await UserService.getUser('1');
    expect(user.name).toBe('DevFlow');
    expect(mockFetch).toHaveBeenCalledTimes(1);
  });
});

Detected Breaking Changes & Semantic Shifts (1)

Mock Replacement: jest.fn() -> vi.fn()

info

Vitest replaces the global `jest` namespace with `vi` (`vi.fn()`, `vi.spyOn()`, `vi.mock()`).

Resolution: Import `vi` from "vitest": `import { vi } from "vitest";`.

How to Migrate from Jest to Vitest

1
Paste your Jest unit test file or jest.config.js.
2
The migrator swaps `jest.fn()` and `jest.spyOn()` for Vitest `vi` equivalents.
3
Global test assertions are converted to explicit ESM imports for TypeScript safety.
4
Run `bun test` or `vitest run` to execute test suites instantly.

Run Vitest in CI Pipeline

.github/workflows/test.yml

name: Tests
on: [push, pull_request]
jobs:
  test:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - run: bun install
      - run: bun run test:run

Run Migration via Terminal CLI

Perform identical migration routines across entire directories or repositories in your local terminal:

devflow migrate jest-to-vitest -i tests/

Webpack 5Vite

Migrate Webpack 5 Config to Vite (10x Faster HMR)

Convert webpack.config.js bundles into lightning-fast Vite configs (vite.config.ts). Eliminate multi-minute cold starts and reload delays.

Explore migration

npm / Node.jsBun Runtime

Migrate npm package.json to Bun Runtime & Scripts

Instantly migrate npm scripts, dependencies, and configurations to Bun. Optimize script execution speeds and strip obsolete transpilations.

Explore migration

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Frequently Asked Questions

Can Vitest run Jest test files without modifying code?: Yes! By adding `test: { globals: true }` in `vitest.config.ts`, global `describe`, `it`, and `expect` remain globally available.

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